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href="#">What’s New In Python 3.6</a><ul> <li><a class="reference internal" href="#summary-release-highlights">Summary – Release highlights</a></li> <li><a class="reference internal" href="#new-features">New Features</a><ul> <li><a class="reference internal" href="#pep-498-formatted-string-literals">PEP 498: Formatted string literals</a></li> <li><a class="reference internal" href="#pep-526-syntax-for-variable-annotations">PEP 526: Syntax for variable annotations</a></li> <li><a class="reference internal" href="#pep-515-underscores-in-numeric-literals">PEP 515: Underscores in Numeric Literals</a></li> <li><a class="reference internal" href="#pep-525-asynchronous-generators">PEP 525: Asynchronous Generators</a></li> <li><a class="reference internal" href="#pep-530-asynchronous-comprehensions">PEP 530: Asynchronous Comprehensions</a></li> <li><a class="reference internal" href="#pep-487-simpler-customization-of-class-creation">PEP 487: Simpler customization of class creation</a></li> <li><a class="reference internal" href="#pep-487-descriptor-protocol-enhancements">PEP 487: Descriptor Protocol Enhancements</a></li> <li><a class="reference internal" href="#pep-519-adding-a-file-system-path-protocol">PEP 519: Adding a file system path protocol</a></li> <li><a class="reference internal" href="#pep-495-local-time-disambiguation">PEP 495: Local Time Disambiguation</a></li> <li><a class="reference internal" href="#pep-529-change-windows-filesystem-encoding-to-utf-8">PEP 529: Change Windows filesystem encoding to UTF-8</a></li> <li><a class="reference internal" href="#pep-528-change-windows-console-encoding-to-utf-8">PEP 528: Change Windows console encoding to UTF-8</a></li> <li><a class="reference internal" href="#pep-520-preserving-class-attribute-definition-order">PEP 520: Preserving Class Attribute Definition Order</a></li> <li><a class="reference internal" href="#pep-468-preserving-keyword-argument-order">PEP 468: Preserving Keyword Argument Order</a></li> <li><a class="reference internal" href="#new-dict-implementation">New dict implementation</a></li> <li><a class="reference internal" href="#pep-523-adding-a-frame-evaluation-api-to-cpython">PEP 523: Adding a frame evaluation API to CPython</a></li> <li><a class="reference internal" href="#pythonmalloc-environment-variable">PYTHONMALLOC environment variable</a></li> <li><a class="reference internal" href="#dtrace-and-systemtap-probing-support">DTrace and SystemTap probing support</a></li> </ul> </li> <li><a class="reference internal" href="#other-language-changes">Other Language Changes</a></li> <li><a class="reference internal" href="#new-modules">New Modules</a><ul> <li><a class="reference internal" href="#secrets">secrets</a></li> </ul> </li> <li><a class="reference internal" href="#improved-modules">Improved Modules</a><ul> <li><a class="reference internal" href="#array">array</a></li> <li><a class="reference internal" href="#ast">ast</a></li> <li><a class="reference internal" href="#asyncio">asyncio</a></li> <li><a class="reference internal" href="#binascii">binascii</a></li> <li><a class="reference internal" href="#cmath">cmath</a></li> <li><a class="reference internal" href="#collections">collections</a></li> <li><a class="reference internal" href="#concurrent-futures">concurrent.futures</a></li> <li><a class="reference internal" href="#contextlib">contextlib</a></li> <li><a class="reference internal" href="#datetime">datetime</a></li> <li><a class="reference internal" href="#decimal">decimal</a></li> <li><a class="reference internal" href="#distutils">distutils</a></li> <li><a class="reference internal" href="#email">email</a></li> <li><a class="reference internal" href="#encodings">encodings</a></li> <li><a class="reference internal" href="#enum">enum</a></li> <li><a class="reference internal" href="#faulthandler">faulthandler</a></li> <li><a class="reference internal" href="#fileinput">fileinput</a></li> <li><a class="reference internal" href="#hashlib">hashlib</a></li> <li><a class="reference internal" href="#http-client">http.client</a></li> <li><a class="reference internal" href="#idlelib-and-idle">idlelib and IDLE</a></li> <li><a class="reference internal" href="#importlib">importlib</a></li> <li><a class="reference internal" href="#inspect">inspect</a></li> <li><a class="reference internal" href="#json">json</a></li> <li><a class="reference internal" href="#logging">logging</a></li> <li><a class="reference internal" href="#math">math</a></li> <li><a class="reference internal" href="#multiprocessing">multiprocessing</a></li> <li><a class="reference internal" href="#os">os</a></li> <li><a class="reference internal" href="#pathlib">pathlib</a></li> <li><a class="reference internal" href="#pdb">pdb</a></li> <li><a class="reference internal" href="#pickle">pickle</a></li> <li><a class="reference internal" href="#pickletools">pickletools</a></li> <li><a class="reference internal" href="#pydoc">pydoc</a></li> <li><a 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class="reference internal" href="#time">time</a></li> <li><a class="reference internal" href="#timeit">timeit</a></li> <li><a class="reference internal" href="#tkinter">tkinter</a></li> <li><a class="reference internal" href="#traceback">traceback</a></li> <li><a class="reference internal" href="#tracemalloc">tracemalloc</a></li> <li><a class="reference internal" href="#typing">typing</a></li> <li><a class="reference internal" href="#unicodedata">unicodedata</a></li> <li><a class="reference internal" href="#unittest-mock">unittest.mock</a></li> <li><a class="reference internal" href="#urllib-request">urllib.request</a></li> <li><a class="reference internal" href="#urllib-robotparser">urllib.robotparser</a></li> <li><a class="reference internal" href="#venv">venv</a></li> <li><a class="reference internal" href="#warnings">warnings</a></li> <li><a class="reference internal" href="#winreg">winreg</a></li> <li><a class="reference internal" href="#winsound">winsound</a></li> <li><a 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class="document"> <div class="documentwrapper"> <div class="bodywrapper"> <div class="body" role="main"> <section id="what-s-new-in-python-3-6"> <h1>What’s New In Python 3.6<a class="headerlink" href="#what-s-new-in-python-3-6" title="Link to this heading">¶</a></h1> <dl class="field-list simple"> <dt class="field-odd">Editors:</dt> <dd class="field-odd">Elvis Pranskevichus <<a class="reference external" href="mailto:elvis%40magic.io">elvis@magic.io</a>>, Yury Selivanov <<a class="reference external" href="mailto:yury%40magic.io">yury@magic.io</a>> </dd> </dl> This article explains the new features in Python 3.6, compared to 3.5. Python 3.6 was released on December 23, 2016. See the <a class="reference external" href="https://docs.python.org/3.6/whatsnew/changelog.html">changelog</a> for a full list of changes. <div class="admonition seealso"> See also <a class="pep reference external" href="https://peps.python.org/pep-0494/">PEP 494</a> - Python 3.6 Release Schedule </div> <section id="summary-release-highlights"> <h2>Summary – Release highlights<a class="headerlink" href="#summary-release-highlights" title="Link to this heading">¶</a></h2> New syntax features: <ul class="simple"> <li><a class="reference internal" href="#whatsnew36-pep498">PEP 498</a>, formatted string literals.</li> <li><a class="reference internal" href="#whatsnew36-pep515">PEP 515</a>, underscores in numeric literals.</li> <li><a class="reference internal" href="#whatsnew36-pep526">PEP 526</a>, syntax for variable annotations.</li> <li><a class="reference internal" href="#whatsnew36-pep525">PEP 525</a>, asynchronous generators.</li> <li><a class="reference internal" href="#whatsnew36-pep530">PEP 530</a>: asynchronous comprehensions.</li> </ul> New library modules: <ul class="simple"> <li><a class="reference internal" href="../library/secrets.html#module-secrets" title="secrets: Generate secure random numbers for managing secrets."><code class="xref py py-mod docutils literal notranslate">secrets</code></a>: <a class="reference internal" href="#whatsnew36-pep506">PEP 506 – Adding A Secrets Module To The Standard Library</a>.</li> </ul> CPython implementation improvements: <ul class="simple"> <li>The <a class="reference internal" href="../library/stdtypes.html#typesmapping">dict</a> type has been reimplemented to use a <a class="reference internal" href="#whatsnew36-compactdict">more compact representation</a> based on <a class="reference external" href="https://mail.python.org/pipermail/python-dev/2012-December/123028.html">a proposal by Raymond Hettinger</a> and similar to the <a class="reference external" href="https://morepypy.blogspot.com/2015/01/faster-more-memory-efficient-and-more.html">PyPy dict implementation</a>. This resulted in dictionaries using 20% to 25% less memory when compared to Python 3.5.</li> <li>Customization of class creation has been simplified with the <a class="reference internal" href="#whatsnew36-pep487">new protocol</a>.</li> <li>The class attribute definition order is <a class="reference internal" href="#whatsnew36-pep520">now preserved</a>.</li> <li>The order of elements in <code class="docutils literal notranslate">**kwargs</code> now <a class="reference internal" href="#whatsnew36-pep468">corresponds to the order</a> in which keyword arguments were passed to the function.</li> <li>DTrace and SystemTap <a class="reference internal" href="#whatsnew36-tracing">probing support</a> has been added.</li> <li>The new <a class="reference internal" href="#whatsnew36-pythonmalloc">PYTHONMALLOC</a> environment variable can now be used to debug the interpreter memory allocation and access errors.</li> </ul> Significant improvements in the standard library: <ul class="simple"> <li>The <a class="reference internal" href="../library/asyncio.html#module-asyncio" title="asyncio: Asynchronous I/O."><code class="xref py py-mod docutils literal notranslate">asyncio</code></a> module has received new features, significant usability and performance improvements, and a fair amount of bug fixes. Starting with Python 3.6 the <code class="docutils literal notranslate">asyncio</code> module is no longer provisional and its API is considered stable.</li> <li>A new <a class="reference internal" href="#whatsnew36-pep519">file system path protocol</a> has been implemented to support <a class="reference internal" href="../glossary.html#term-path-like-object">path-like objects</a>. All standard library functions operating on paths have been updated to work with the new protocol.</li> <li>The <a class="reference internal" href="../library/datetime.html#module-datetime" title="datetime: Basic date and time types."><code class="xref py py-mod docutils literal notranslate">datetime</code></a> module has gained support for <a class="reference internal" href="#whatsnew36-pep495">Local Time Disambiguation</a>.</li> <li>The <a class="reference internal" href="../library/typing.html#module-typing" title="typing: Support for type hints (see :pep:`484`)."><code class="xref py py-mod docutils literal notranslate">typing</code></a> module received a number of <a class="reference internal" href="#whatsnew36-typing">improvements</a>.</li> <li>The <a class="reference internal" href="../library/tracemalloc.html#module-tracemalloc" title="tracemalloc: Trace memory allocations."><code class="xref py py-mod docutils literal notranslate">tracemalloc</code></a> module has been significantly reworked and is now used to provide better output for <a class="reference internal" href="../library/exceptions.html#ResourceWarning" title="ResourceWarning"><code class="xref py py-exc docutils literal notranslate">ResourceWarning</code></a> as well as provide better diagnostics for memory allocation errors. See the <a class="reference internal" href="#whatsnew36-pythonmalloc">PYTHONMALLOC section</a> for more information.</li> </ul> Security improvements: <ul class="simple"> <li>The new <a class="reference internal" href="../library/secrets.html#module-secrets" title="secrets: Generate secure random numbers for managing secrets."><code class="xref py py-mod docutils literal notranslate">secrets</code></a> module has been added to simplify the generation of cryptographically strong pseudo-random numbers suitable for managing secrets such as account authentication, tokens, and similar.</li> <li>On Linux, <a class="reference internal" href="../library/os.html#os.urandom" title="os.urandom"><code class="xref py py-func docutils literal notranslate">os.urandom()</code></a> now blocks until the system urandom entropy pool is initialized to increase the security. See the <a class="pep reference external" href="https://peps.python.org/pep-0524/">PEP 524</a> for the rationale.</li> <li>The <a class="reference internal" href="../library/hashlib.html#module-hashlib" title="hashlib: Secure hash and message digest algorithms."><code class="xref py py-mod docutils literal notranslate">hashlib</code></a> and <a class="reference internal" href="../library/ssl.html#module-ssl" title="ssl: TLS/SSL wrapper for socket objects"><code class="xref py py-mod docutils literal notranslate">ssl</code></a> modules now support OpenSSL 1.1.0.</li> <li>The default settings and feature set of the <a class="reference internal" href="../library/ssl.html#module-ssl" title="ssl: TLS/SSL wrapper for socket objects"><code class="xref py py-mod docutils literal notranslate">ssl</code></a> module have been improved.</li> <li>The <a class="reference internal" href="../library/hashlib.html#module-hashlib" title="hashlib: Secure hash and message digest algorithms."><code class="xref py py-mod docutils literal notranslate">hashlib</code></a> module received support for the BLAKE2, SHA-3 and SHAKE hash algorithms and the <a class="reference internal" href="../library/hashlib.html#hashlib.scrypt" title="hashlib.scrypt"><code class="xref py py-func docutils literal notranslate">scrypt()</code></a> key derivation function.</li> </ul> Windows improvements: <ul class="simple"> <li><a class="reference internal" href="#whatsnew36-pep528">PEP 528</a> and <a class="reference internal" href="#whatsnew36-pep529">PEP 529</a>, Windows filesystem and console encoding changed to UTF-8.</li> <li>The <code class="docutils literal notranslate">py.exe</code> launcher, when used interactively, no longer prefers Python 2 over Python 3 when the user doesn’t specify a version (via command line arguments or a config file). Handling of shebang lines remains unchanged - “python” refers to Python 2 in that case.</li> <li><code class="docutils literal notranslate">python.exe</code> and <code class="docutils literal notranslate">pythonw.exe</code> have been marked as long-path aware, which means that the 260 character path limit may no longer apply. See <a class="reference internal" href="../using/windows.html#max-path">removing the MAX_PATH limitation</a> for details.</li> <li>A <code class="docutils literal notranslate">._pth</code> file can be added to force isolated mode and fully specify all search paths to avoid registry and environment lookup. See <a class="reference internal" href="../using/windows.html#windows-finding-modules">the documentation</a> for more information.</li> <li>A <code class="docutils literal notranslate">python36.zip</code> file now works as a landmark to infer <a class="reference internal" href="../using/cmdline.html#envvar-PYTHONHOME"><code class="xref std std-envvar docutils literal notranslate">PYTHONHOME</code></a>. See <a class="reference internal" href="../using/windows.html#windows-finding-modules">the documentation</a> for more information.</li> </ul> </section> <section id="new-features"> <h2>New Features<a class="headerlink" href="#new-features" title="Link to this heading">¶</a></h2> <section id="pep-498-formatted-string-literals"> <h3>PEP 498: Formatted string literals<a class="headerlink" href="#pep-498-formatted-string-literals" title="Link to this heading">¶</a></h3> <a class="pep reference external" href="https://peps.python.org/pep-0498/">PEP 498</a> introduces a new kind of string literals: f-strings, or <a class="reference internal" href="../reference/lexical_analysis.html#f-strings">formatted string literals</a>. Formatted string literals are prefixed with <code class="docutils literal notranslate">'f'</code> and are similar to the format strings accepted by <a class="reference internal" href="../library/stdtypes.html#str.format" title="str.format"><code class="xref py py-meth docutils literal notranslate">str.format()</code></a>. They contain replacement fields surrounded by curly braces. The replacement fields are expressions, which are evaluated at run time, and then formatted using the <a class="reference internal" href="../library/functions.html#format" title="format"><code class="xref py py-func docutils literal notranslate">format()</code></a> protocol: <div class="highlight-python3 notranslate"><div class="highlight"><pre>>>> name = "Fred" >>> f"He said his name is {name}." 'He said his name is Fred.' >>> width = 10 >>> precision = 4 >>> value = decimal.Decimal("12.34567") >>> f"result: {value:{width}.{precision}}" # nested fields 'result: 12.35' </pre></div> </div> <div class="admonition seealso"> See also <dl class="simple"> <dt><a class="pep reference external" href="https://peps.python.org/pep-0498/">PEP 498</a> – Literal String Interpolation.</dt><dd>PEP written and implemented by Eric V. Smith. </dd> </dl> <a class="reference internal" href="../reference/lexical_analysis.html#f-strings">Feature documentation</a>. </div> </section> <section id="pep-526-syntax-for-variable-annotations"> <h3>PEP 526: Syntax for variable annotations<a class="headerlink" href="#pep-526-syntax-for-variable-annotations" title="Link to this heading">¶</a></h3> <a class="pep reference external" href="https://peps.python.org/pep-0484/">PEP 484</a> introduced the standard for type annotations of function parameters, a.k.a. type hints. This PEP adds syntax to Python for annotating the types of variables including class variables and instance variables: <div class="highlight-python3 notranslate"><div class="highlight"><pre>primes: List[int] = [] captain: str # Note: no initial value! class Starship: stats: Dict[str, int] = {} </pre></div> </div> Just as for function annotations, the Python interpreter does not attach any particular meaning to variable annotations and only stores them in the <code class="docutils literal notranslate">__annotations__</code> attribute of a class or module. In contrast to variable declarations in statically typed languages, the goal of annotation syntax is to provide an easy way to specify structured type metadata for third party tools and libraries via the abstract syntax tree and the <code class="docutils literal notranslate">__annotations__</code> attribute. <div class="admonition seealso"> See also <dl class="simple"> <dt><a class="pep reference external" href="https://peps.python.org/pep-0526/">PEP 526</a> – Syntax for variable annotations.</dt><dd>PEP written by Ryan Gonzalez, Philip House, Ivan Levkivskyi, Lisa Roach, and Guido van Rossum. Implemented by Ivan Levkivskyi. </dd> </dl> Tools that use or will use the new syntax: <a class="reference external" href="https://www.mypy-lang.org/">mypy</a>, <a class="reference external" href="https://github.com/google/pytype">pytype</a>, PyCharm, etc. </div> </section> <section id="pep-515-underscores-in-numeric-literals"> <h3>PEP 515: Underscores in Numeric Literals<a class="headerlink" href="#pep-515-underscores-in-numeric-literals" title="Link to this heading">¶</a></h3> <a class="pep reference external" href="https://peps.python.org/pep-0515/">PEP 515</a> adds the ability to use underscores in numeric literals for improved readability. For example: <div class="highlight-python3 notranslate"><div class="highlight"><pre>>>> 1_000_000_000_000_000 1000000000000000 >>> 0x_FF_FF_FF_FF 4294967295 </pre></div> </div> Single underscores are allowed between digits and after any base specifier. Leading, trailing, or multiple underscores in a row are not allowed. The <a class="reference internal" href="../library/string.html#formatspec">string formatting</a> language also now has support for the <code class="docutils literal notranslate">'_'</code> option to signal the use of an underscore for a thousands separator for floating-point presentation types and for integer presentation type <code class="docutils literal notranslate">'d'</code>. For integer presentation types <code class="docutils literal notranslate">'b'</code>, <code class="docutils literal notranslate">'o'</code>, <code class="docutils literal notranslate">'x'</code>, and <code class="docutils literal notranslate">'X'</code>, underscores will be inserted every 4 digits: <div class="highlight-python3 notranslate"><div class="highlight"><pre>>>> '{:_}'.format(1000000) '1_000_000' >>> '{:_x}'.format(0xFFFFFFFF) 'ffff_ffff' </pre></div> </div> <div class="admonition seealso"> See also <dl class="simple"> <dt><a class="pep reference external" href="https://peps.python.org/pep-0515/">PEP 515</a> – Underscores in Numeric Literals</dt><dd>PEP written by Georg Brandl and Serhiy Storchaka. </dd> </dl> </div> </section> <section id="pep-525-asynchronous-generators"> <h3>PEP 525: Asynchronous Generators<a class="headerlink" href="#pep-525-asynchronous-generators" title="Link to this heading">¶</a></h3> <a class="pep reference external" href="https://peps.python.org/pep-0492/">PEP 492</a> introduced support for native coroutines and <code class="docutils literal notranslate">async</code> / <code class="docutils literal notranslate">await</code> syntax to Python 3.5. A notable limitation of the Python 3.5 implementation is that it was not possible to use <code class="docutils literal notranslate">await</code> and <code class="docutils literal notranslate">yield</code> in the same function body. In Python 3.6 this restriction has been lifted, making it possible to define asynchronous generators: <div class="highlight-python3 notranslate"><div class="highlight"><pre>async def ticker(delay, to): """Yield numbers from 0 to *to* every *delay* seconds.""" for i in range(to): yield i await asyncio.sleep(delay) </pre></div> </div> The new syntax allows for faster and more concise code. <div class="admonition seealso"> See also <dl class="simple"> <dt><a class="pep reference external" href="https://peps.python.org/pep-0525/">PEP 525</a> – Asynchronous Generators</dt><dd>PEP written and implemented by Yury Selivanov. </dd> </dl> </div> </section> <section id="pep-530-asynchronous-comprehensions"> <h3>PEP 530: Asynchronous Comprehensions<a class="headerlink" href="#pep-530-asynchronous-comprehensions" title="Link to this heading">¶</a></h3> <a class="pep reference external" href="https://peps.python.org/pep-0530/">PEP 530</a> adds support for using <code class="docutils literal notranslate">async for</code> in list, set, dict comprehensions and generator expressions: <div class="highlight-python3 notranslate"><div class="highlight"><pre>result = [i async for i in aiter() if i % 2] </pre></div> </div> Additionally, <code class="docutils literal notranslate">await</code> expressions are supported in all kinds of comprehensions: <div class="highlight-python3 notranslate"><div class="highlight"><pre>result = [await fun() for fun in funcs if await condition()] </pre></div> </div> <div class="admonition seealso"> See also <dl class="simple"> <dt><a class="pep reference external" href="https://peps.python.org/pep-0530/">PEP 530</a> – Asynchronous Comprehensions</dt><dd>PEP written and implemented by Yury Selivanov. </dd> </dl> </div> </section> <section id="pep-487-simpler-customization-of-class-creation"> <h3>PEP 487: Simpler customization of class creation<a class="headerlink" href="#pep-487-simpler-customization-of-class-creation" title="Link to this heading">¶</a></h3> It is now possible to customize subclass creation without using a metaclass. The new <code class="docutils literal notranslate">__init_subclass__</code> classmethod will be called on the base class whenever a new subclass is created: <div class="highlight-python3 notranslate"><div class="highlight"><pre>class PluginBase: subclasses = [] def __init_subclass__(cls, **kwargs): super().__init_subclass__(**kwargs) cls.subclasses.append(cls) class Plugin1(PluginBase): pass class Plugin2(PluginBase): pass </pre></div> </div> In order to allow zero-argument <a class="reference internal" href="../library/functions.html#super" title="super"><code class="xref py py-func docutils literal notranslate">super()</code></a> calls to work correctly from <a class="reference internal" href="../reference/datamodel.html#object.__init_subclass__" title="object.__init_subclass__"><code class="xref py py-meth docutils literal notranslate">__init_subclass__()</code></a> implementations, custom metaclasses must ensure that the new <code class="docutils literal notranslate">__classcell__</code> namespace entry is propagated to <code class="docutils literal notranslate">type.__new__</code> (as described in <a class="reference internal" href="../reference/datamodel.html#class-object-creation">Creating the class object</a>). <div class="admonition seealso"> See also <dl class="simple"> <dt><a class="pep reference external" href="https://peps.python.org/pep-0487/">PEP 487</a> – Simpler customization of class creation</dt><dd>PEP written and implemented by Martin Teichmann. </dd> </dl> <a class="reference internal" href="../reference/datamodel.html#class-customization">Feature documentation</a> </div> </section> <section id="pep-487-descriptor-protocol-enhancements"> <h3>PEP 487: Descriptor Protocol Enhancements<a class="headerlink" href="#pep-487-descriptor-protocol-enhancements" title="Link to this heading">¶</a></h3> <a class="pep reference external" href="https://peps.python.org/pep-0487/">PEP 487</a> extends the descriptor protocol to include the new optional <a class="reference internal" href="../reference/datamodel.html#object.__set_name__" title="object.__set_name__"><code class="xref py py-meth docutils literal notranslate">__set_name__()</code></a> method. Whenever a new class is defined, the new method will be called on all descriptors included in the definition, providing them with a reference to the class being defined and the name given to the descriptor within the class namespace. In other words, instances of descriptors can now know the attribute name of the descriptor in the owner class: <div class="highlight-python3 notranslate"><div class="highlight"><pre>class IntField: def __get__(self, instance, owner): return instance.__dict__[self.name] def __set__(self, instance, value): if not isinstance(value, int): raise ValueError(f'expecting integer in {self.name}') instance.__dict__[self.name] = value # this is the new initializer: def __set_name__(self, owner, name): self.name = name class Model: int_field = IntField() </pre></div> </div> <div class="admonition seealso"> See also <dl class="simple"> <dt><a class="pep reference external" href="https://peps.python.org/pep-0487/">PEP 487</a> – Simpler customization of class creation</dt><dd>PEP written and implemented by Martin Teichmann. </dd> </dl> <a class="reference internal" href="../reference/datamodel.html#descriptors">Feature documentation</a> </div> </section> <section id="pep-519-adding-a-file-system-path-protocol"> <h3>PEP 519: Adding a file system path protocol<a class="headerlink" href="#pep-519-adding-a-file-system-path-protocol" title="Link to this heading">¶</a></h3> File system paths have historically been represented as <a class="reference internal" href="../library/stdtypes.html#str" title="str"><code class="xref py py-class docutils literal notranslate">str</code></a> or <a class="reference internal" href="../library/stdtypes.html#bytes" title="bytes"><code class="xref py py-class docutils literal notranslate">bytes</code></a> objects. This has led to people who write code which operate on file system paths to assume that such objects are only one of those two types (an <a class="reference internal" href="../library/functions.html#int" title="int"><code class="xref py py-class docutils literal notranslate">int</code></a> representing a file descriptor does not count as that is not a file path). Unfortunately that assumption prevents alternative object representations of file system paths like <a class="reference internal" href="../library/pathlib.html#module-pathlib" title="pathlib: Object-oriented filesystem paths"><code class="xref py py-mod docutils literal notranslate">pathlib</code></a> from working with pre-existing code, including Python’s standard library. To fix this situation, a new interface represented by <a class="reference internal" href="../library/os.html#os.PathLike" title="os.PathLike"><code class="xref py py-class docutils literal notranslate">os.PathLike</code></a> has been defined. By implementing the <a class="reference internal" href="../library/os.html#os.PathLike.__fspath__" title="os.PathLike.__fspath__"><code class="xref py py-meth docutils literal notranslate">__fspath__()</code></a> method, an object signals that it represents a path. An object can then provide a low-level representation of a file system path as a <a class="reference internal" href="../library/stdtypes.html#str" title="str"><code class="xref py py-class docutils literal notranslate">str</code></a> or <a class="reference internal" href="../library/stdtypes.html#bytes" title="bytes"><code class="xref py py-class docutils literal notranslate">bytes</code></a> object. This means an object is considered <a class="reference internal" href="../glossary.html#term-path-like-object">path-like</a> if it implements <a class="reference internal" href="../library/os.html#os.PathLike" title="os.PathLike"><code class="xref py py-class docutils literal notranslate">os.PathLike</code></a> or is a <a class="reference internal" href="../library/stdtypes.html#str" title="str"><code class="xref py py-class docutils literal notranslate">str</code></a> or <a class="reference internal" href="../library/stdtypes.html#bytes" title="bytes"><code class="xref py py-class docutils literal notranslate">bytes</code></a> object which represents a file system path. Code can use <a class="reference internal" href="../library/os.html#os.fspath" title="os.fspath"><code class="xref py py-func docutils literal notranslate">os.fspath()</code></a>, <a class="reference internal" href="../library/os.html#os.fsdecode" title="os.fsdecode"><code class="xref py py-func docutils literal notranslate">os.fsdecode()</code></a>, or <a class="reference internal" href="../library/os.html#os.fsencode" title="os.fsencode"><code class="xref py py-func docutils literal notranslate">os.fsencode()</code></a> to explicitly get a <a class="reference internal" href="../library/stdtypes.html#str" title="str"><code class="xref py py-class docutils literal notranslate">str</code></a> and/or <a class="reference internal" href="../library/stdtypes.html#bytes" title="bytes"><code class="xref py py-class docutils literal notranslate">bytes</code></a> representation of a path-like object. The built-in <a class="reference internal" href="../library/functions.html#open" title="open"><code class="xref py py-func docutils literal notranslate">open()</code></a> function has been updated to accept <a class="reference internal" href="../library/os.html#os.PathLike" title="os.PathLike"><code class="xref py py-class docutils literal notranslate">os.PathLike</code></a> objects, as have all relevant functions in the <a class="reference internal" href="../library/os.html#module-os" title="os: Miscellaneous operating system interfaces."><code class="xref py py-mod docutils literal notranslate">os</code></a> and <a class="reference internal" href="../library/os.path.html#module-os.path" title="os.path: Operations on pathnames."><code class="xref py py-mod docutils literal notranslate">os.path</code></a> modules, and most other functions and classes in the standard library. The <a class="reference internal" href="../library/os.html#os.DirEntry" title="os.DirEntry"><code class="xref py py-class docutils literal notranslate">os.DirEntry</code></a> class and relevant classes in <a class="reference internal" href="../library/pathlib.html#module-pathlib" title="pathlib: Object-oriented filesystem paths"><code class="xref py py-mod docutils literal notranslate">pathlib</code></a> have also been updated to implement <a class="reference internal" href="../library/os.html#os.PathLike" title="os.PathLike"><code class="xref py py-class docutils literal notranslate">os.PathLike</code></a>. The hope is that updating the fundamental functions for operating on file system paths will lead to third-party code to implicitly support all <a class="reference internal" href="../glossary.html#term-path-like-object">path-like objects</a> without any code changes, or at least very minimal ones (e.g. calling <a class="reference internal" href="../library/os.html#os.fspath" title="os.fspath"><code class="xref py py-func docutils literal notranslate">os.fspath()</code></a> at the beginning of code before operating on a path-like object). Here are some examples of how the new interface allows for <a class="reference internal" href="../library/pathlib.html#pathlib.Path" title="pathlib.Path"><code class="xref py py-class docutils literal notranslate">pathlib.Path</code></a> to be used more easily and transparently with pre-existing code: <div class="highlight-python3 notranslate"><div class="highlight"><pre>>>> import pathlib >>> with open(pathlib.Path("README")) as f: ... contents = f.read() ... >>> import os.path >>> os.path.splitext(pathlib.Path("some_file.txt")) ('some_file', '.txt') >>> os.path.join("/a/b", pathlib.Path("c")) '/a/b/c' >>> import os >>> os.fspath(pathlib.Path("some_file.txt")) 'some_file.txt' </pre></div> </div> (Implemented by Brett Cannon, Ethan Furman, Dusty Phillips, and Jelle Zijlstra.) <div class="admonition seealso"> See also <dl class="simple"> <dt><a class="pep reference external" href="https://peps.python.org/pep-0519/">PEP 519</a> – Adding a file system path protocol</dt><dd>PEP written by Brett Cannon and Koos Zevenhoven. </dd> </dl> </div> </section> <section id="pep-495-local-time-disambiguation"> <h3>PEP 495: Local Time Disambiguation<a class="headerlink" href="#pep-495-local-time-disambiguation" title="Link to this heading">¶</a></h3> In most world locations, there have been and will be times when local clocks are moved back. In those times, intervals are introduced in which local clocks show the same time twice in the same day. In these situations, the information displayed on a local clock (or stored in a Python datetime instance) is insufficient to identify a particular moment in time. <a class="pep reference external" href="https://peps.python.org/pep-0495/">PEP 495</a> adds the new fold attribute to instances of <a class="reference internal" href="../library/datetime.html#datetime.datetime" title="datetime.datetime"><code class="xref py py-class docutils literal notranslate">datetime.datetime</code></a> and <a class="reference internal" href="../library/datetime.html#datetime.time" title="datetime.time"><code class="xref py py-class docutils literal notranslate">datetime.time</code></a> classes to differentiate between two moments in time for which local times are the same: <div class="highlight-python3 notranslate"><div class="highlight"><pre>>>> u0 = datetime(2016, 11, 6, 4, tzinfo=timezone.utc) >>> for i in range(4): ... u = u0 + i*HOUR ... t = u.astimezone(Eastern) ... print(u.time(), 'UTC =', t.time(), t.tzname(), t.fold) ... 04:00:00 UTC = 00:00:00 EDT 0 05:00:00 UTC = 01:00:00 EDT 0 06:00:00 UTC = 01:00:00 EST 1 07:00:00 UTC = 02:00:00 EST 0 </pre></div> </div> The values of the <a class="reference internal" href="../library/datetime.html#datetime.datetime.fold" title="datetime.datetime.fold"><code class="xref py py-attr docutils literal notranslate">fold</code></a> attribute have the value <code class="docutils literal notranslate">0</code> for all instances except those that represent the second (chronologically) moment in time in an ambiguous case. <div class="admonition seealso"> See also <dl class="simple"> <dt><a class="pep reference external" href="https://peps.python.org/pep-0495/">PEP 495</a> – Local Time Disambiguation</dt><dd>PEP written by Alexander Belopolsky and Tim Peters, implementation by Alexander Belopolsky. </dd> </dl> </div> </section> <section id="pep-529-change-windows-filesystem-encoding-to-utf-8"> <h3>PEP 529: Change Windows filesystem encoding to UTF-8<a class="headerlink" href="#pep-529-change-windows-filesystem-encoding-to-utf-8" title="Link to this heading">¶</a></h3> Representing filesystem paths is best performed with str (Unicode) rather than bytes. However, there are some situations where using bytes is sufficient and correct. Prior to Python 3.6, data loss could result when using bytes paths on Windows. With this change, using bytes to represent paths is now supported on Windows, provided those bytes are encoded with the encoding returned by <a class="reference internal" href="../library/sys.html#sys.getfilesystemencoding" title="sys.getfilesystemencoding"><code class="xref py py-func docutils literal notranslate">sys.getfilesystemencoding()</code></a>, which now defaults to <code class="docutils literal notranslate">'utf-8'</code>. Applications that do not use str to represent paths should use <a class="reference internal" href="../library/os.html#os.fsencode" title="os.fsencode"><code class="xref py py-func docutils literal notranslate">os.fsencode()</code></a> and <a class="reference internal" href="../library/os.html#os.fsdecode" title="os.fsdecode"><code class="xref py py-func docutils literal notranslate">os.fsdecode()</code></a> to ensure their bytes are correctly encoded. To revert to the previous behaviour, set <a class="reference internal" href="../using/cmdline.html#envvar-PYTHONLEGACYWINDOWSFSENCODING"><code class="xref std std-envvar docutils literal notranslate">PYTHONLEGACYWINDOWSFSENCODING</code></a> or call <a class="reference internal" href="../library/sys.html#sys._enablelegacywindowsfsencoding" title="sys._enablelegacywindowsfsencoding"><code class="xref py py-func docutils literal notranslate">sys._enablelegacywindowsfsencoding()</code></a>. See <a class="pep reference external" href="https://peps.python.org/pep-0529/">PEP 529</a> for more information and discussion of code modifications that may be required. </section> <section id="pep-528-change-windows-console-encoding-to-utf-8"> <h3>PEP 528: Change Windows console encoding to UTF-8<a class="headerlink" href="#pep-528-change-windows-console-encoding-to-utf-8" title="Link to this heading">¶</a></h3> The default console on Windows will now accept all Unicode characters and provide correctly read str objects to Python code. <code class="docutils literal notranslate">sys.stdin</code>, <code class="docutils literal notranslate">sys.stdout</code> and <code class="docutils literal notranslate">sys.stderr</code> now default to utf-8 encoding. This change only applies when using an interactive console, and not when redirecting files or pipes. To revert to the previous behaviour for interactive console use, set <a class="reference internal" href="../using/cmdline.html#envvar-PYTHONLEGACYWINDOWSSTDIO"><code class="xref std std-envvar docutils literal notranslate">PYTHONLEGACYWINDOWSSTDIO</code></a>. <div class="admonition seealso"> See also <dl class="simple"> <dt><a class="pep reference external" href="https://peps.python.org/pep-0528/">PEP 528</a> – Change Windows console encoding to UTF-8</dt><dd>PEP written and implemented by Steve Dower. </dd> </dl> </div> </section> <section id="pep-520-preserving-class-attribute-definition-order"> <h3>PEP 520: Preserving Class Attribute Definition Order<a class="headerlink" href="#pep-520-preserving-class-attribute-definition-order" title="Link to this heading">¶</a></h3> Attributes in a class definition body have a natural ordering: the same order in which the names appear in the source. This order is now preserved in the new class’s <a class="reference internal" href="../reference/datamodel.html#type.__dict__" title="type.__dict__"><code class="xref py py-attr docutils literal notranslate">__dict__</code></a> attribute. Also, the effective default class execution namespace (returned from <a class="reference internal" href="../reference/datamodel.html#prepare">type.__prepare__()</a>) is now an insertion-order-preserving mapping. <div class="admonition seealso"> See also <dl class="simple"> <dt><a class="pep reference external" href="https://peps.python.org/pep-0520/">PEP 520</a> – Preserving Class Attribute Definition Order</dt><dd>PEP written and implemented by Eric Snow. </dd> </dl> </div> </section> <section id="pep-468-preserving-keyword-argument-order"> <h3>PEP 468: Preserving Keyword Argument Order<a class="headerlink" href="#pep-468-preserving-keyword-argument-order" title="Link to this heading">¶</a></h3> <code class="docutils literal notranslate">**kwargs</code> in a function signature is now guaranteed to be an insertion-order-preserving mapping. <div class="admonition seealso"> See also <dl class="simple"> <dt><a class="pep reference external" href="https://peps.python.org/pep-0468/">PEP 468</a> – Preserving Keyword Argument Order</dt><dd>PEP written and implemented by Eric Snow. </dd> </dl> </div> </section> <section id="new-dict-implementation"> <h3>New <a class="reference internal" href="../library/stdtypes.html#typesmapping">dict</a> implementation<a class="headerlink" href="#new-dict-implementation" title="Link to this heading">¶</a></h3> The <a class="reference internal" href="../library/stdtypes.html#typesmapping">dict</a> type now uses a “compact” representation based on <a class="reference external" href="https://mail.python.org/pipermail/python-dev/2012-December/123028.html">a proposal by Raymond Hettinger</a> which was <a class="reference external" href="https://morepypy.blogspot.com/2015/01/faster-more-memory-efficient-and-more.html">first implemented by PyPy</a>. The memory usage of the new <a class="reference internal" href="../library/stdtypes.html#dict" title="dict"><code class="xref py py-func docutils literal notranslate">dict()</code></a> is between 20% and 25% smaller compared to Python 3.5. The order-preserving aspect of this new implementation is considered an implementation detail and should not be relied upon (this may change in the future, but it is desired to have this new dict implementation in the language for a few releases before changing the language spec to mandate order-preserving semantics for all current and future Python implementations; this also helps preserve backwards-compatibility with older versions of the language where random iteration order is still in effect, e.g. Python 3.5). (Contributed by INADA Naoki in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=27350">bpo-27350</a>. Idea <a class="reference external" href="https://mail.python.org/pipermail/python-dev/2012-December/123028.html">originally suggested by Raymond Hettinger</a>.) </section> <section id="pep-523-adding-a-frame-evaluation-api-to-cpython"> <h3>PEP 523: Adding a frame evaluation API to CPython<a class="headerlink" href="#pep-523-adding-a-frame-evaluation-api-to-cpython" title="Link to this heading">¶</a></h3> While Python provides extensive support to customize how code executes, one place it has not done so is in the evaluation of frame objects. If you wanted some way to intercept frame evaluation in Python there really wasn’t any way without directly manipulating function pointers for defined functions. <a class="pep reference external" href="https://peps.python.org/pep-0523/">PEP 523</a> changes this by providing an API to make frame evaluation pluggable at the C level. This will allow for tools such as debuggers and JITs to intercept frame evaluation before the execution of Python code begins. This enables the use of alternative evaluation implementations for Python code, tracking frame evaluation, etc. This API is not part of the limited C API and is marked as private to signal that usage of this API is expected to be limited and only applicable to very select, low-level use-cases. Semantics of the API will change with Python as necessary. <div class="admonition seealso"> See also <dl class="simple"> <dt><a class="pep reference external" href="https://peps.python.org/pep-0523/">PEP 523</a> – Adding a frame evaluation API to CPython</dt><dd>PEP written by Brett Cannon and Dino Viehland. </dd> </dl> </div> </section> <section id="pythonmalloc-environment-variable"> <h3>PYTHONMALLOC environment variable<a class="headerlink" href="#pythonmalloc-environment-variable" title="Link to this heading">¶</a></h3> The new <a class="reference internal" href="../using/cmdline.html#envvar-PYTHONMALLOC"><code class="xref std std-envvar docutils literal notranslate">PYTHONMALLOC</code></a> environment variable allows setting the Python memory allocators and installing debug hooks. It is now possible to install debug hooks on Python memory allocators on Python compiled in release mode using <code class="docutils literal notranslate">PYTHONMALLOC=debug</code>. Effects of debug hooks: <ul class="simple"> <li>Newly allocated memory is filled with the byte <code class="docutils literal notranslate">0xCB</code></li> <li>Freed memory is filled with the byte <code class="docutils literal notranslate">0xDB</code></li> <li>Detect violations of the Python memory allocator API. For example, <a class="reference internal" href="../c-api/memory.html#c.PyObject_Free" title="PyObject_Free"><code class="xref c c-func docutils literal notranslate">PyObject_Free()</code></a> called on a memory block allocated by <a class="reference internal" href="../c-api/memory.html#c.PyMem_Malloc" title="PyMem_Malloc"><code class="xref c c-func docutils literal notranslate">PyMem_Malloc()</code></a>.</li> <li>Detect writes before the start of a buffer (buffer underflows)</li> <li>Detect writes after the end of a buffer (buffer overflows)</li> <li>Check that the <a class="reference internal" href="../glossary.html#term-global-interpreter-lock">GIL</a> is held when allocator functions of <a class="reference internal" href="../c-api/memory.html#c.PYMEM_DOMAIN_OBJ" title="PYMEM_DOMAIN_OBJ"><code class="xref c c-macro docutils literal notranslate">PYMEM_DOMAIN_OBJ</code></a> (ex: <a class="reference internal" href="../c-api/memory.html#c.PyObject_Malloc" title="PyObject_Malloc"><code class="xref c c-func docutils literal notranslate">PyObject_Malloc()</code></a>) and <a class="reference internal" href="../c-api/memory.html#c.PYMEM_DOMAIN_MEM" title="PYMEM_DOMAIN_MEM"><code class="xref c c-macro docutils literal notranslate">PYMEM_DOMAIN_MEM</code></a> (ex: <a class="reference internal" href="../c-api/memory.html#c.PyMem_Malloc" title="PyMem_Malloc"><code class="xref c c-func docutils literal notranslate">PyMem_Malloc()</code></a>) domains are called.</li> </ul> Checking if the GIL is held is also a new feature of Python 3.6. See the <a class="reference internal" href="../c-api/memory.html#c.PyMem_SetupDebugHooks" title="PyMem_SetupDebugHooks"><code class="xref c c-func docutils literal notranslate">PyMem_SetupDebugHooks()</code></a> function for debug hooks on Python memory allocators. It is now also possible to force the usage of the <code class="xref c c-func docutils literal notranslate">malloc()</code> allocator of the C library for all Python memory allocations using <code class="docutils literal notranslate">PYTHONMALLOC=malloc</code>. This is helpful when using external memory debuggers like Valgrind on a Python compiled in release mode. On error, the debug hooks on Python memory allocators now use the <a class="reference internal" href="../library/tracemalloc.html#module-tracemalloc" title="tracemalloc: Trace memory allocations."><code class="xref py py-mod docutils literal notranslate">tracemalloc</code></a> module to get the traceback where a memory block was allocated. Example of fatal error on buffer overflow using <code class="docutils literal notranslate">python3.6 -X tracemalloc=5</code> (store 5 frames in traces): <div class="highlight-python3 notranslate"><div class="highlight"><pre>Debug memory block at address p=0x7fbcd41666f8: API 'o' 4 bytes originally requested The 7 pad bytes at p-7 are FORBIDDENBYTE, as expected. The 8 pad bytes at tail=0x7fbcd41666fc are not all FORBIDDENBYTE (0xfb): at tail+0: 0x02 *** OUCH at tail+1: 0xfb at tail+2: 0xfb at tail+3: 0xfb at tail+4: 0xfb at tail+5: 0xfb at tail+6: 0xfb at tail+7: 0xfb The block was made by call #1233329 to debug malloc/realloc. Data at p: 1a 2b 30 00 Memory block allocated at (most recent call first): File "test/test_bytes.py", line 323 File "unittest/case.py", line 600 File "unittest/case.py", line 648 File "unittest/suite.py", line 122 File "unittest/suite.py", line 84 Fatal Python error: bad trailing pad byte Current thread 0x00007fbcdbd32700 (most recent call first): File "test/test_bytes.py", line 323 in test_hex File "unittest/case.py", line 600 in run File "unittest/case.py", line 648 in __call__ File "unittest/suite.py", line 122 in run File "unittest/suite.py", line 84 in __call__ File "unittest/suite.py", line 122 in run File "unittest/suite.py", line 84 in __call__ ... </pre></div> </div> (Contributed by Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=26516">bpo-26516</a> and <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=26564">bpo-26564</a>.) </section> <section id="dtrace-and-systemtap-probing-support"> <h3>DTrace and SystemTap probing support<a class="headerlink" href="#dtrace-and-systemtap-probing-support" title="Link to this heading">¶</a></h3> Python can now be built <code class="docutils literal notranslate">--with-dtrace</code> which enables static markers for the following events in the interpreter: <ul class="simple"> <li>function call/return</li> <li>garbage collection started/finished</li> <li>line of code executed.</li> </ul> This can be used to instrument running interpreters in production, without the need to recompile specific <a class="reference internal" href="../using/configure.html#debug-build">debug builds</a> or providing application-specific profiling/debugging code. More details in <a class="reference internal" href="../howto/instrumentation.html#instrumentation">Instrumenting CPython with DTrace and SystemTap</a>. The current implementation is tested on Linux and macOS. Additional markers may be added in the future. (Contributed by Łukasz Langa in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=21590">bpo-21590</a>, based on patches by Jesús Cea Avión, David Malcolm, and Nikhil Benesch.) </section> </section> <section id="other-language-changes"> <h2>Other Language Changes<a class="headerlink" href="#other-language-changes" title="Link to this heading">¶</a></h2> Some smaller changes made to the core Python language are: <ul class="simple"> <li>A <code class="docutils literal notranslate">global</code> or <code class="docutils literal notranslate">nonlocal</code> statement must now textually appear before the first use of the affected name in the same scope. Previously this was a <a class="reference internal" href="../library/exceptions.html#SyntaxWarning" title="SyntaxWarning"><code class="xref py py-exc docutils literal notranslate">SyntaxWarning</code></a>.</li> <li>It is now possible to set a <a class="reference internal" href="../reference/datamodel.html#specialnames">special method</a> to <code class="docutils literal notranslate">None</code> to indicate that the corresponding operation is not available. For example, if a class sets <code class="xref py py-meth docutils literal notranslate">__iter__()</code> to <code class="docutils literal notranslate">None</code>, the class is not iterable. (Contributed by Andrew Barnert and Ivan Levkivskyi in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=25958">bpo-25958</a>.)</li> <li>Long sequences of repeated traceback lines are now abbreviated as <code class="docutils literal notranslate">"[Previous line repeated {count} more times]"</code> (see <a class="reference internal" href="#whatsnew36-traceback">traceback</a> for an example). (Contributed by Emanuel Barry in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=26823">bpo-26823</a>.)</li> <li>Import now raises the new exception <a class="reference internal" href="../library/exceptions.html#ModuleNotFoundError" title="ModuleNotFoundError"><code class="xref py py-exc docutils literal notranslate">ModuleNotFoundError</code></a> (subclass of <a class="reference internal" href="../library/exceptions.html#ImportError" title="ImportError"><code class="xref py py-exc docutils literal notranslate">ImportError</code></a>) when it cannot find a module. Code that currently checks for ImportError (in try-except) will still work. (Contributed by Eric Snow in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=15767">bpo-15767</a>.)</li> <li>Class methods relying on zero-argument <code class="docutils literal notranslate">super()</code> will now work correctly when called from metaclass methods during class creation. (Contributed by Martin Teichmann in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=23722">bpo-23722</a>.)</li> </ul> </section> <section id="new-modules"> <h2>New Modules<a class="headerlink" href="#new-modules" title="Link to this heading">¶</a></h2> <section id="secrets"> <h3>secrets<a class="headerlink" href="#secrets" title="Link to this heading">¶</a></h3> The main purpose of the new <a class="reference internal" href="../library/secrets.html#module-secrets" title="secrets: Generate secure random numbers for managing secrets."><code class="xref py py-mod docutils literal notranslate">secrets</code></a> module is to provide an obvious way to reliably generate cryptographically strong pseudo-random values suitable for managing secrets, such as account authentication, tokens, and similar. <div class="admonition warning"> Warning Note that the pseudo-random generators in the <a class="reference internal" href="../library/random.html#module-random" title="random: Generate pseudo-random numbers with various common distributions."><code class="xref py py-mod docutils literal notranslate">random</code></a> module should NOT be used for security purposes. Use <a class="reference internal" href="../library/secrets.html#module-secrets" title="secrets: Generate secure random numbers for managing secrets."><code class="xref py py-mod docutils literal notranslate">secrets</code></a> on Python 3.6+ and <a class="reference internal" href="../library/os.html#os.urandom" title="os.urandom"><code class="xref py py-func docutils literal notranslate">os.urandom()</code></a> on Python 3.5 and earlier. </div> <div class="admonition seealso"> See also <dl class="simple"> <dt><a class="pep reference external" href="https://peps.python.org/pep-0506/">PEP 506</a> – Adding A Secrets Module To The Standard Library</dt><dd>PEP written and implemented by Steven D’Aprano. </dd> </dl> </div> </section> </section> <section id="improved-modules"> <h2>Improved Modules<a class="headerlink" href="#improved-modules" title="Link to this heading">¶</a></h2> <section id="array"> <h3>array<a class="headerlink" href="#array" title="Link to this heading">¶</a></h3> Exhausted iterators of <a class="reference internal" href="../library/array.html#array.array" title="array.array"><code class="xref py py-class docutils literal notranslate">array.array</code></a> will now stay exhausted even if the iterated array is extended. This is consistent with the behavior of other mutable sequences. Contributed by Serhiy Storchaka in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=26492">bpo-26492</a>. </section> <section id="ast"> <h3>ast<a class="headerlink" href="#ast" title="Link to this heading">¶</a></h3> The new <a class="reference internal" href="../library/ast.html#ast.Constant" title="ast.Constant"><code class="xref py py-class docutils literal notranslate">ast.Constant</code></a> AST node has been added. It can be used by external AST optimizers for the purposes of constant folding. Contributed by Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=26146">bpo-26146</a>. </section> <section id="asyncio"> <h3>asyncio<a class="headerlink" href="#asyncio" title="Link to this heading">¶</a></h3> Starting with Python 3.6 the <code class="docutils literal notranslate">asyncio</code> module is no longer provisional and its API is considered stable. Notable changes in the <a class="reference internal" href="../library/asyncio.html#module-asyncio" title="asyncio: Asynchronous I/O."><code class="xref py py-mod docutils literal notranslate">asyncio</code></a> module since Python 3.5.0 (all backported to 3.5.x due to the provisional status): <ul class="simple"> <li>The <a class="reference internal" href="../library/asyncio-eventloop.html#asyncio.get_event_loop" title="asyncio.get_event_loop"><code class="xref py py-func docutils literal notranslate">get_event_loop()</code></a> function has been changed to always return the currently running loop when called from coroutines and callbacks. (Contributed by Yury Selivanov in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=28613">bpo-28613</a>.)</li> <li>The <a class="reference internal" href="../library/asyncio-future.html#asyncio.ensure_future" title="asyncio.ensure_future"><code class="xref py py-func docutils literal notranslate">ensure_future()</code></a> function and all functions that use it, such as <a class="reference internal" href="../library/asyncio-eventloop.html#asyncio.loop.run_until_complete" title="asyncio.loop.run_until_complete"><code class="xref py py-meth docutils literal notranslate">loop.run_until_complete()</code></a>, now accept all kinds of <a class="reference internal" href="../glossary.html#term-awaitable">awaitable objects</a>. (Contributed by Yury Selivanov.)</li> <li>New <a class="reference internal" href="../library/asyncio-task.html#asyncio.run_coroutine_threadsafe" title="asyncio.run_coroutine_threadsafe"><code class="xref py py-func docutils literal notranslate">run_coroutine_threadsafe()</code></a> function to submit coroutines to event loops from other threads. (Contributed by Vincent Michel.)</li> <li>New <a class="reference internal" href="../library/asyncio-protocol.html#asyncio.BaseTransport.is_closing" title="asyncio.BaseTransport.is_closing"><code class="xref py py-meth docutils literal notranslate">Transport.is_closing()</code></a> method to check if the transport is closing or closed. (Contributed by Yury Selivanov.)</li> <li>The <a class="reference internal" href="../library/asyncio-eventloop.html#asyncio.loop.create_server" title="asyncio.loop.create_server"><code class="xref py py-meth docutils literal notranslate">loop.create_server()</code></a> method can now accept a list of hosts. (Contributed by Yann Sionneau.)</li> <li>New <a class="reference internal" href="../library/asyncio-eventloop.html#asyncio.loop.create_future" title="asyncio.loop.create_future"><code class="xref py py-meth docutils literal notranslate">loop.create_future()</code></a> method to create Future objects. This allows alternative event loop implementations, such as <a class="reference external" href="https://github.com/MagicStack/uvloop">uvloop</a>, to provide a faster <a class="reference internal" href="../library/asyncio-future.html#asyncio.Future" title="asyncio.Future"><code class="xref py py-class docutils literal notranslate">asyncio.Future</code></a> implementation. (Contributed by Yury Selivanov in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=27041">bpo-27041</a>.)</li> <li>New <a class="reference internal" href="../library/asyncio-eventloop.html#asyncio.loop.get_exception_handler" title="asyncio.loop.get_exception_handler"><code class="xref py py-meth docutils literal notranslate">loop.get_exception_handler()</code></a> method to get the current exception handler. (Contributed by Yury Selivanov in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=27040">bpo-27040</a>.)</li> <li>New <a class="reference internal" href="../library/asyncio-stream.html#asyncio.StreamReader.readuntil" title="asyncio.StreamReader.readuntil"><code class="xref py py-meth docutils literal notranslate">StreamReader.readuntil()</code></a> method to read data from the stream until a separator bytes sequence appears. (Contributed by Mark Korenberg.)</li> <li>The performance of <a class="reference internal" href="../library/asyncio-stream.html#asyncio.StreamReader.readexactly" title="asyncio.StreamReader.readexactly"><code class="xref py py-meth docutils literal notranslate">StreamReader.readexactly()</code></a> has been improved. (Contributed by Mark Korenberg in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=28370">bpo-28370</a>.)</li> <li>The <a class="reference internal" href="../library/asyncio-eventloop.html#asyncio.loop.getaddrinfo" title="asyncio.loop.getaddrinfo"><code class="xref py py-meth docutils literal notranslate">loop.getaddrinfo()</code></a> method is optimized to avoid calling the system <code class="docutils literal notranslate">getaddrinfo</code> function if the address is already resolved. (Contributed by A. Jesse Jiryu Davis.)</li> <li>The <a class="reference internal" href="../library/asyncio-eventloop.html#asyncio.loop.stop" title="asyncio.loop.stop"><code class="xref py py-meth docutils literal notranslate">loop.stop()</code></a> method has been changed to stop the loop immediately after the current iteration. Any new callbacks scheduled as a result of the last iteration will be discarded. (Contributed by Guido van Rossum in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=25593">bpo-25593</a>.)</li> <li><code class="xref py py-meth docutils literal notranslate">Future.set_exception</code> will now raise <a class="reference internal" href="../library/exceptions.html#TypeError" title="TypeError"><code class="xref py py-exc docutils literal notranslate">TypeError</code></a> when passed an instance of the <a class="reference internal" href="../library/exceptions.html#StopIteration" title="StopIteration"><code class="xref py py-exc docutils literal notranslate">StopIteration</code></a> exception. (Contributed by Chris Angelico in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=26221">bpo-26221</a>.)</li> <li>New <a class="reference internal" href="../library/asyncio-eventloop.html#asyncio.loop.connect_accepted_socket" title="asyncio.loop.connect_accepted_socket"><code class="xref py py-meth docutils literal notranslate">loop.connect_accepted_socket()</code></a> method to be used by servers that accept connections outside of asyncio, but that use asyncio to handle them. (Contributed by Jim Fulton in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=27392">bpo-27392</a>.)</li> <li><code class="docutils literal notranslate">TCP_NODELAY</code> flag is now set for all TCP transports by default. (Contributed by Yury Selivanov in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=27456">bpo-27456</a>.)</li> <li>New <a class="reference internal" href="../library/asyncio-eventloop.html#asyncio.loop.shutdown_asyncgens" title="asyncio.loop.shutdown_asyncgens"><code class="xref py py-meth docutils literal notranslate">loop.shutdown_asyncgens()</code></a> to properly close pending asynchronous generators before closing the loop. (Contributed by Yury Selivanov in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=28003">bpo-28003</a>.)</li> <li><a class="reference internal" href="../library/asyncio-future.html#asyncio.Future" title="asyncio.Future"><code class="xref py py-class docutils literal notranslate">Future</code></a> and <a class="reference internal" href="../library/asyncio-task.html#asyncio.Task" title="asyncio.Task"><code class="xref py py-class docutils literal notranslate">Task</code></a> classes now have an optimized C implementation which makes asyncio code up to 30% faster. (Contributed by Yury Selivanov and INADA Naoki in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=26081">bpo-26081</a> and <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=28544">bpo-28544</a>.)</li> </ul> </section> <section id="binascii"> <h3>binascii<a class="headerlink" href="#binascii" title="Link to this heading">¶</a></h3> The <a class="reference internal" href="../library/binascii.html#binascii.b2a_base64" title="binascii.b2a_base64"><code class="xref py py-func docutils literal notranslate">b2a_base64()</code></a> function now accepts an optional newline keyword argument to control whether the newline character is appended to the return value. (Contributed by Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=25357">bpo-25357</a>.) </section> <section id="cmath"> <h3>cmath<a class="headerlink" href="#cmath" title="Link to this heading">¶</a></h3> The new <a class="reference internal" href="../library/cmath.html#cmath.tau" title="cmath.tau"><code class="xref py py-const docutils literal notranslate">cmath.tau</code></a> (τ) constant has been added. (Contributed by Lisa Roach in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=12345">bpo-12345</a>, see <a class="pep reference external" href="https://peps.python.org/pep-0628/">PEP 628</a> for details.) New constants: <a class="reference internal" href="../library/cmath.html#cmath.inf" title="cmath.inf"><code class="xref py py-const docutils literal notranslate">cmath.inf</code></a> and <a class="reference internal" href="../library/cmath.html#cmath.nan" title="cmath.nan"><code class="xref py py-const docutils literal notranslate">cmath.nan</code></a> to match <a class="reference internal" href="../library/math.html#math.inf" title="math.inf"><code class="xref py py-const docutils literal notranslate">math.inf</code></a> and <a class="reference internal" href="../library/math.html#math.nan" title="math.nan"><code class="xref py py-const docutils literal notranslate">math.nan</code></a>, and also <a class="reference internal" href="../library/cmath.html#cmath.infj" title="cmath.infj"><code class="xref py py-const docutils literal notranslate">cmath.infj</code></a> and <a class="reference internal" href="../library/cmath.html#cmath.nanj" title="cmath.nanj"><code class="xref py py-const docutils literal notranslate">cmath.nanj</code></a> to match the format used by complex repr. (Contributed by Mark Dickinson in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=23229">bpo-23229</a>.) </section> <section id="collections"> <h3>collections<a class="headerlink" href="#collections" title="Link to this heading">¶</a></h3> The new <a class="reference internal" href="../library/collections.abc.html#collections.abc.Collection" title="collections.abc.Collection"><code class="xref py py-class docutils literal notranslate">Collection</code></a> abstract base class has been added to represent sized iterable container classes. (Contributed by Ivan Levkivskyi, docs by Neil Girdhar in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=27598">bpo-27598</a>.) The new <a class="reference internal" href="../library/collections.abc.html#collections.abc.Reversible" title="collections.abc.Reversible"><code class="xref py py-class docutils literal notranslate">Reversible</code></a> abstract base class represents iterable classes that also provide the <code class="xref py py-meth docutils literal notranslate">__reversed__()</code> method. (Contributed by Ivan Levkivskyi in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=25987">bpo-25987</a>.) The new <a class="reference internal" href="../library/collections.abc.html#collections.abc.AsyncGenerator" title="collections.abc.AsyncGenerator"><code class="xref py py-class docutils literal notranslate">AsyncGenerator</code></a> abstract base class represents asynchronous generators. (Contributed by Yury Selivanov in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=28720">bpo-28720</a>.) The <a class="reference internal" href="../library/collections.html#collections.namedtuple" title="collections.namedtuple"><code class="xref py py-func docutils literal notranslate">namedtuple()</code></a> function now accepts an optional keyword argument module, which, when specified, is used for the <a class="reference internal" href="../reference/datamodel.html#type.__module__" title="type.__module__"><code class="xref py py-attr docutils literal notranslate">__module__</code></a> attribute of the returned named tuple class. (Contributed by Raymond Hettinger in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=17941">bpo-17941</a>.) The verbose and rename arguments for <a class="reference internal" href="../library/collections.html#collections.namedtuple" title="collections.namedtuple"><code class="xref py py-func docutils literal notranslate">namedtuple()</code></a> are now keyword-only. (Contributed by Raymond Hettinger in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=25628">bpo-25628</a>.) Recursive <a class="reference internal" href="../library/collections.html#collections.deque" title="collections.deque"><code class="xref py py-class docutils literal notranslate">collections.deque</code></a> instances can now be pickled. (Contributed by Serhiy Storchaka in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=26482">bpo-26482</a>.) </section> <section id="concurrent-futures"> <h3>concurrent.futures<a class="headerlink" href="#concurrent-futures" title="Link to this heading">¶</a></h3> The <a class="reference internal" href="../library/concurrent.futures.html#concurrent.futures.ThreadPoolExecutor" title="concurrent.futures.ThreadPoolExecutor"><code class="xref py py-class docutils literal notranslate">ThreadPoolExecutor</code></a> class constructor now accepts an optional thread_name_prefix argument to make it possible to customize the names of the threads created by the pool. (Contributed by Gregory P. Smith in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=27664">bpo-27664</a>.) </section> <section id="contextlib"> <h3>contextlib<a class="headerlink" href="#contextlib" title="Link to this heading">¶</a></h3> The <a class="reference internal" href="../library/contextlib.html#contextlib.AbstractContextManager" title="contextlib.AbstractContextManager"><code class="xref py py-class docutils literal notranslate">contextlib.AbstractContextManager</code></a> class has been added to provide an abstract base class for context managers. It provides a sensible default implementation for <code class="docutils literal notranslate">__enter__()</code> which returns <code class="docutils literal notranslate">self</code> and leaves <code class="docutils literal notranslate">__exit__()</code> an abstract method. A matching class has been added to the <a class="reference internal" href="../library/typing.html#module-typing" title="typing: Support for type hints (see :pep:`484`)."><code class="xref py py-mod docutils literal notranslate">typing</code></a> module as <a class="reference internal" href="../library/typing.html#typing.ContextManager" title="typing.ContextManager"><code class="xref py py-class docutils literal notranslate">typing.ContextManager</code></a>. (Contributed by Brett Cannon in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=25609">bpo-25609</a>.) </section> <section id="datetime"> <h3>datetime<a class="headerlink" href="#datetime" title="Link to this heading">¶</a></h3> The <a class="reference internal" href="../library/datetime.html#datetime.datetime" title="datetime.datetime"><code class="xref py py-class docutils literal notranslate">datetime</code></a> and <a class="reference internal" href="../library/datetime.html#datetime.time" title="datetime.time"><code class="xref py py-class docutils literal notranslate">time</code></a> classes have the new <code class="xref py py-attr docutils literal notranslate">fold</code> attribute used to disambiguate local time when necessary. Many functions in the <a class="reference internal" href="../library/datetime.html#module-datetime" title="datetime: Basic date and time types."><code class="xref py py-mod docutils literal notranslate">datetime</code></a> have been updated to support local time disambiguation. See <a class="reference internal" href="#whatsnew36-pep495">Local Time Disambiguation</a> section for more information. (Contributed by Alexander Belopolsky in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=24773">bpo-24773</a>.) The <a class="reference internal" href="../library/datetime.html#datetime.datetime.strftime" title="datetime.datetime.strftime"><code class="xref py py-meth docutils literal notranslate">datetime.strftime()</code></a> and <a class="reference internal" href="../library/datetime.html#datetime.date.strftime" title="datetime.date.strftime"><code class="xref py py-meth docutils literal notranslate">date.strftime()</code></a> methods now support ISO 8601 date directives <code class="docutils literal notranslate">%G</code>, <code class="docutils literal notranslate">%u</code> and <code class="docutils literal notranslate">%V</code>. (Contributed by Ashley Anderson in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=12006">bpo-12006</a>.) The <a class="reference internal" href="../library/datetime.html#datetime.datetime.isoformat" title="datetime.datetime.isoformat"><code class="xref py py-func docutils literal notranslate">datetime.isoformat()</code></a> function now accepts an optional timespec argument that specifies the number of additional components of the time value to include. (Contributed by Alessandro Cucci and Alexander Belopolsky in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=19475">bpo-19475</a>.) The <a class="reference internal" href="../library/datetime.html#datetime.datetime.combine" title="datetime.datetime.combine"><code class="xref py py-meth docutils literal notranslate">datetime.combine()</code></a> now accepts an optional tzinfo argument. (Contributed by Alexander Belopolsky in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=27661">bpo-27661</a>.) </section> <section id="decimal"> <h3>decimal<a class="headerlink" href="#decimal" title="Link to this heading">¶</a></h3> New <a class="reference internal" href="../library/decimal.html#decimal.Decimal.as_integer_ratio" title="decimal.Decimal.as_integer_ratio"><code class="xref py py-meth docutils literal notranslate">Decimal.as_integer_ratio()</code></a> method that returns a pair <code class="docutils literal notranslate">(n, d)</code> of integers that represent the given <a class="reference internal" href="../library/decimal.html#decimal.Decimal" title="decimal.Decimal"><code class="xref py py-class docutils literal notranslate">Decimal</code></a> instance as a fraction, in lowest terms and with a positive denominator: <div class="highlight-python3 notranslate"><div class="highlight"><pre>>>> Decimal('-3.14').as_integer_ratio() (-157, 50) </pre></div> </div> (Contributed by Stefan Krah amd Mark Dickinson in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=25928">bpo-25928</a>.) </section> <section id="distutils"> <h3>distutils<a class="headerlink" href="#distutils" title="Link to this heading">¶</a></h3> The <code class="docutils literal notranslate">default_format</code> attribute has been removed from <code class="docutils literal notranslate">distutils.command.sdist.sdist</code> and the <code class="docutils literal notranslate">formats</code> attribute defaults to <code class="docutils literal notranslate">['gztar']</code>. Although not anticipated, any code relying on the presence of <code class="docutils literal notranslate">default_format</code> may need to be adapted. See <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=27819">bpo-27819</a> for more details. </section> <section id="email"> <h3>email<a class="headerlink" href="#email" title="Link to this heading">¶</a></h3> The new email API, enabled via the policy keyword to various constructors, is no longer provisional. The <a class="reference internal" href="../library/email.html#module-email" title="email: Package supporting the parsing, manipulating, and generating email messages."><code class="xref py py-mod docutils literal notranslate">email</code></a> documentation has been reorganized and rewritten to focus on the new API, while retaining the old documentation for the legacy API. (Contributed by R. David Murray in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=24277">bpo-24277</a>.) The <a class="reference internal" href="../library/email.mime.html#module-email.mime" title="email.mime: Build MIME messages."><code class="xref py py-mod docutils literal notranslate">email.mime</code></a> classes now all accept an optional policy keyword. (Contributed by Berker Peksag in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=27331">bpo-27331</a>.) The <a class="reference internal" href="../library/email.generator.html#email.generator.DecodedGenerator" title="email.generator.DecodedGenerator"><code class="xref py py-class docutils literal notranslate">DecodedGenerator</code></a> now supports the policy keyword. There is a new <a class="reference internal" href="../library/email.policy.html#module-email.policy" title="email.policy: Controlling the parsing and generating of messages"><code class="xref py py-mod docutils literal notranslate">policy</code></a> attribute, <a class="reference internal" href="../library/email.policy.html#email.policy.Policy.message_factory" title="email.policy.Policy.message_factory"><code class="xref py py-attr docutils literal notranslate">message_factory</code></a>, that controls what class is used by default when the parser creates new message objects. For the <a class="reference internal" href="../library/email.policy.html#email.policy.compat32" title="email.policy.compat32"><code class="xref py py-attr docutils literal notranslate">email.policy.compat32</code></a> policy this is <a class="reference internal" href="../library/email.compat32-message.html#email.message.Message" title="email.message.Message"><code class="xref py py-class docutils literal notranslate">Message</code></a>, for the new policies it is <a class="reference internal" href="../library/email.message.html#email.message.EmailMessage" title="email.message.EmailMessage"><code class="xref py py-class docutils literal notranslate">EmailMessage</code></a>. (Contributed by R. David Murray in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=20476">bpo-20476</a>.) </section> <section id="encodings"> <h3>encodings<a class="headerlink" href="#encodings" title="Link to this heading">¶</a></h3> On Windows, added the <code class="docutils literal notranslate">'oem'</code> encoding to use <code class="docutils literal notranslate">CP_OEMCP</code>, and the <code class="docutils literal notranslate">'ansi'</code> alias for the existing <code class="docutils literal notranslate">'mbcs'</code> encoding, which uses the <code class="docutils literal notranslate">CP_ACP</code> code page. (Contributed by Steve Dower in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=27959">bpo-27959</a>.) </section> <section id="enum"> <h3>enum<a class="headerlink" href="#enum" title="Link to this heading">¶</a></h3> Two new enumeration base classes have been added to the <a class="reference internal" href="../library/enum.html#module-enum" title="enum: Implementation of an enumeration class."><code class="xref py py-mod docutils literal notranslate">enum</code></a> module: <a class="reference internal" href="../library/enum.html#enum.Flag" title="enum.Flag"><code class="xref py py-class docutils literal notranslate">Flag</code></a> and <code class="xref py py-class docutils literal notranslate">IntFlags</code>. Both are used to define constants that can be combined using the bitwise operators. (Contributed by Ethan Furman in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=23591">bpo-23591</a>.) Many standard library modules have been updated to use the <code class="xref py py-class docutils literal notranslate">IntFlags</code> class for their constants. The new <a class="reference internal" href="../library/enum.html#enum.auto" title="enum.auto"><code class="xref py py-class docutils literal notranslate">enum.auto</code></a> value can be used to assign values to enum members automatically: <div class="highlight-python3 notranslate"><div class="highlight"><pre>>>> from enum import Enum, auto >>> class Color(Enum): ... red = auto() ... blue = auto() ... green = auto() ... >>> list(Color) [<Color.red: 1>, <Color.blue: 2>, <Color.green: 3>] </pre></div> </div> </section> <section id="faulthandler"> <h3>faulthandler<a class="headerlink" href="#faulthandler" title="Link to this heading">¶</a></h3> On Windows, the <a class="reference internal" href="../library/faulthandler.html#module-faulthandler" title="faulthandler: Dump the Python traceback."><code class="xref py py-mod docutils literal notranslate">faulthandler</code></a> module now installs a handler for Windows exceptions: see <a class="reference internal" href="../library/faulthandler.html#faulthandler.enable" title="faulthandler.enable"><code class="xref py py-func docutils literal notranslate">faulthandler.enable()</code></a>. (Contributed by Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=23848">bpo-23848</a>.) </section> <section id="fileinput"> <h3>fileinput<a class="headerlink" href="#fileinput" title="Link to this heading">¶</a></h3> <a class="reference internal" href="../library/fileinput.html#fileinput.hook_encoded" title="fileinput.hook_encoded"><code class="xref py py-func docutils literal notranslate">hook_encoded()</code></a> now supports the errors argument. (Contributed by Joseph Hackman in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=25788">bpo-25788</a>.) </section> <section id="hashlib"> <h3>hashlib<a class="headerlink" href="#hashlib" title="Link to this heading">¶</a></h3> <a class="reference internal" href="../library/hashlib.html#module-hashlib" title="hashlib: Secure hash and message digest algorithms."><code class="xref py py-mod docutils literal notranslate">hashlib</code></a> supports OpenSSL 1.1.0. The minimum recommend version is 1.0.2. (Contributed by Christian Heimes in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=26470">bpo-26470</a>.) BLAKE2 hash functions were added to the module. <a class="reference internal" href="../library/hashlib.html#hashlib.blake2b" title="hashlib.blake2b"><code class="xref py py-func docutils literal notranslate">blake2b()</code></a> and <a class="reference internal" href="../library/hashlib.html#hashlib.blake2s" title="hashlib.blake2s"><code class="xref py py-func docutils literal notranslate">blake2s()</code></a> are always available and support the full feature set of BLAKE2. (Contributed by Christian Heimes in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=26798">bpo-26798</a> based on code by Dmitry Chestnykh and Samuel Neves. Documentation written by Dmitry Chestnykh.) The SHA-3 hash functions <a class="reference internal" href="../library/hashlib.html#hashlib.sha3_224" title="hashlib.sha3_224"><code class="xref py py-func docutils literal notranslate">sha3_224()</code></a>, <a class="reference internal" href="../library/hashlib.html#hashlib.sha3_256" title="hashlib.sha3_256"><code class="xref py py-func docutils literal notranslate">sha3_256()</code></a>, <a class="reference internal" href="../library/hashlib.html#hashlib.sha3_384" title="hashlib.sha3_384"><code class="xref py py-func docutils literal notranslate">sha3_384()</code></a>, <a class="reference internal" href="../library/hashlib.html#hashlib.sha3_512" title="hashlib.sha3_512"><code class="xref py py-func docutils literal notranslate">sha3_512()</code></a>, and SHAKE hash functions <a class="reference internal" href="../library/hashlib.html#hashlib.shake_128" title="hashlib.shake_128"><code class="xref py py-func docutils literal notranslate">shake_128()</code></a> and <a class="reference internal" href="../library/hashlib.html#hashlib.shake_256" title="hashlib.shake_256"><code class="xref py py-func docutils literal notranslate">shake_256()</code></a> were added. (Contributed by Christian Heimes in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=16113">bpo-16113</a>. Keccak Code Package by Guido Bertoni, Joan Daemen, Michaël Peeters, Gilles Van Assche, and Ronny Van Keer.) The password-based key derivation function <a class="reference internal" href="../library/hashlib.html#hashlib.scrypt" title="hashlib.scrypt"><code class="xref py py-func docutils literal notranslate">scrypt()</code></a> is now available with OpenSSL 1.1.0 and newer. (Contributed by Christian Heimes in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=27928">bpo-27928</a>.) </section> <section id="http-client"> <h3>http.client<a class="headerlink" href="#http-client" title="Link to this heading">¶</a></h3> <a class="reference internal" href="../library/http.client.html#http.client.HTTPConnection.request" title="http.client.HTTPConnection.request"><code class="xref py py-meth docutils literal notranslate">HTTPConnection.request()</code></a> and <a class="reference internal" href="../library/http.client.html#http.client.HTTPConnection.endheaders" title="http.client.HTTPConnection.endheaders"><code class="xref py py-meth docutils literal notranslate">endheaders()</code></a> both now support chunked encoding request bodies. (Contributed by Demian Brecht and Rolf Krahl in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=12319">bpo-12319</a>.) </section> <section id="idlelib-and-idle"> <h3>idlelib and IDLE<a class="headerlink" href="#idlelib-and-idle" title="Link to this heading">¶</a></h3> The idlelib package is being modernized and refactored to make IDLE look and work better and to make the code easier to understand, test, and improve. Part of making IDLE look better, especially on Linux and Mac, is using ttk widgets, mostly in the dialogs. As a result, IDLE no longer runs with tcl/tk 8.4. It now requires tcl/tk 8.5 or 8.6. We recommend running the latest release of either. ‘Modernizing’ includes renaming and consolidation of idlelib modules. The renaming of files with partial uppercase names is similar to the renaming of, for instance, Tkinter and TkFont to tkinter and tkinter.font in 3.0. As a result, imports of idlelib files that worked in 3.5 will usually not work in 3.6. At least a module name change will be needed (see idlelib/README.txt), sometimes more. (Name changes contributed by Al Swiegart and Terry Reedy in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=24225">bpo-24225</a>. Most idlelib patches since have been and will be part of the process.) In compensation, the eventual result with be that some idlelib classes will be easier to use, with better APIs and docstrings explaining them. Additional useful information will be added to idlelib when available. New in 3.6.2: Multiple fixes for autocompletion. (Contributed by Louie Lu in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=15786">bpo-15786</a>.) New in 3.6.3: Module Browser (on the File menu, formerly called Class Browser), now displays nested functions and classes in addition to top-level functions and classes. (Contributed by Guilherme Polo, Cheryl Sabella, and Terry Jan Reedy in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=1612262">bpo-1612262</a>.) The IDLE features formerly implemented as extensions have been reimplemented as normal features. Their settings have been moved from the Extensions tab to other dialog tabs. (Contributed by Charles Wohlganger and Terry Jan Reedy in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=27099">bpo-27099</a>.) The Settings dialog (Options, Configure IDLE) has been partly rewritten to improve both appearance and function. (Contributed by Cheryl Sabella and Terry Jan Reedy in multiple issues.) New in 3.6.4: The font sample now includes a selection of non-Latin characters so that users can better see the effect of selecting a particular font. (Contributed by Terry Jan Reedy in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=13802">bpo-13802</a>.) The sample can be edited to include other characters. (Contributed by Serhiy Storchaka in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=31860">bpo-31860</a>.) New in 3.6.6: Editor code context option revised. Box displays all context lines up to maxlines. Clicking on a context line jumps the editor to that line. Context colors for custom themes is added to Highlights tab of Settings dialog. (Contributed by Cheryl Sabella and Terry Jan Reedy in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=33642">bpo-33642</a>, <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=33768">bpo-33768</a>, and <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=33679">bpo-33679</a>.) On Windows, a new API call tells Windows that tk scales for DPI. On Windows 8.1+ or 10, with DPI compatibility properties of the Python binary unchanged, and a monitor resolution greater than 96 DPI, this should make text and lines sharper. It should otherwise have no effect. (Contributed by Terry Jan Reedy in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=33656">bpo-33656</a>.) New in 3.6.7: Output over N lines (50 by default) is squeezed down to a button. N can be changed in the PyShell section of the General page of the Settings dialog. Fewer, but possibly extra long, lines can be squeezed by right clicking on the output. Squeezed output can be expanded in place by double-clicking the button or into the clipboard or a separate window by right-clicking the button. (Contributed by Tal Einat in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=1529353">bpo-1529353</a>.) </section> <section id="importlib"> <h3>importlib<a class="headerlink" href="#importlib" title="Link to this heading">¶</a></h3> Import now raises the new exception <a class="reference internal" href="../library/exceptions.html#ModuleNotFoundError" title="ModuleNotFoundError"><code class="xref py py-exc docutils literal notranslate">ModuleNotFoundError</code></a> (subclass of <a class="reference internal" href="../library/exceptions.html#ImportError" title="ImportError"><code class="xref py py-exc docutils literal notranslate">ImportError</code></a>) when it cannot find a module. Code that current checks for <code class="docutils literal notranslate">ImportError</code> (in try-except) will still work. (Contributed by Eric Snow in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=15767">bpo-15767</a>.) <a class="reference internal" href="../library/importlib.html#importlib.util.LazyLoader" title="importlib.util.LazyLoader"><code class="xref py py-class docutils literal notranslate">importlib.util.LazyLoader</code></a> now calls <a class="reference internal" href="../library/importlib.html#importlib.abc.Loader.create_module" title="importlib.abc.Loader.create_module"><code class="xref py py-meth docutils literal notranslate">create_module()</code></a> on the wrapped loader, removing the restriction that <a class="reference internal" href="../library/importlib.html#importlib.machinery.BuiltinImporter" title="importlib.machinery.BuiltinImporter"><code class="xref py py-class docutils literal notranslate">importlib.machinery.BuiltinImporter</code></a> and <a class="reference internal" href="../library/importlib.html#importlib.machinery.ExtensionFileLoader" title="importlib.machinery.ExtensionFileLoader"><code class="xref py py-class docutils literal notranslate">importlib.machinery.ExtensionFileLoader</code></a> couldn’t be used with <a class="reference internal" href="../library/importlib.html#importlib.util.LazyLoader" title="importlib.util.LazyLoader"><code class="xref py py-class docutils literal notranslate">importlib.util.LazyLoader</code></a>. <a class="reference internal" href="../library/importlib.html#importlib.util.cache_from_source" title="importlib.util.cache_from_source"><code class="xref py py-func docutils literal notranslate">importlib.util.cache_from_source()</code></a>, <a class="reference internal" href="../library/importlib.html#importlib.util.source_from_cache" title="importlib.util.source_from_cache"><code class="xref py py-func docutils literal notranslate">importlib.util.source_from_cache()</code></a>, and <a class="reference internal" href="../library/importlib.html#importlib.util.spec_from_file_location" title="importlib.util.spec_from_file_location"><code class="xref py py-func docutils literal notranslate">importlib.util.spec_from_file_location()</code></a> now accept a <a class="reference internal" href="../glossary.html#term-path-like-object">path-like object</a>. </section> <section id="inspect"> <h3>inspect<a class="headerlink" href="#inspect" title="Link to this heading">¶</a></h3> The <a class="reference internal" href="../library/inspect.html#inspect.signature" title="inspect.signature"><code class="xref py py-func docutils literal notranslate">inspect.signature()</code></a> function now reports the implicit <code class="docutils literal notranslate">.0</code> parameters generated by the compiler for comprehension and generator expression scopes as if they were positional-only parameters called <code class="docutils literal notranslate">implicit0</code>. (Contributed by Jelle Zijlstra in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=19611">bpo-19611</a>.) To reduce code churn when upgrading from Python 2.7 and the legacy <code class="xref py py-func docutils literal notranslate">inspect.getargspec()</code> API, the previously documented deprecation of <a class="reference internal" href="../library/inspect.html#inspect.getfullargspec" title="inspect.getfullargspec"><code class="xref py py-func docutils literal notranslate">inspect.getfullargspec()</code></a> has been reversed. While this function is convenient for single/source Python 2/3 code bases, the richer <a class="reference internal" href="../library/inspect.html#inspect.signature" title="inspect.signature"><code class="xref py py-func docutils literal notranslate">inspect.signature()</code></a> interface remains the recommended approach for new code. (Contributed by Nick Coghlan in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=27172">bpo-27172</a>) </section> <section id="json"> <h3>json<a class="headerlink" href="#json" title="Link to this heading">¶</a></h3> <a class="reference internal" href="../library/json.html#json.load" title="json.load"><code class="xref py py-func docutils literal notranslate">json.load()</code></a> and <a class="reference internal" href="../library/json.html#json.loads" title="json.loads"><code class="xref py py-func docutils literal notranslate">json.loads()</code></a> now support binary input. Encoded JSON should be represented using either UTF-8, UTF-16, or UTF-32. (Contributed by Serhiy Storchaka in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=17909">bpo-17909</a>.) </section> <section id="logging"> <h3>logging<a class="headerlink" href="#logging" title="Link to this heading">¶</a></h3> The new <a class="reference internal" href="../library/logging.handlers.html#logging.handlers.WatchedFileHandler.reopenIfNeeded" title="logging.handlers.WatchedFileHandler.reopenIfNeeded"><code class="xref py py-meth docutils literal notranslate">WatchedFileHandler.reopenIfNeeded()</code></a> method has been added to add the ability to check if the log file needs to be reopened. (Contributed by Marian Horban in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=24884">bpo-24884</a>.) </section> <section id="math"> <h3>math<a class="headerlink" href="#math" title="Link to this heading">¶</a></h3> The tau (τ) constant has been added to the <a class="reference internal" href="../library/math.html#module-math" title="math: Mathematical functions (sin() etc.)."><code class="xref py py-mod docutils literal notranslate">math</code></a> and <a class="reference internal" href="../library/cmath.html#module-cmath" title="cmath: Mathematical functions for complex numbers."><code class="xref py py-mod docutils literal notranslate">cmath</code></a> modules. (Contributed by Lisa Roach in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=12345">bpo-12345</a>, see <a class="pep reference external" href="https://peps.python.org/pep-0628/">PEP 628</a> for details.) </section> <section id="multiprocessing"> <h3>multiprocessing<a class="headerlink" href="#multiprocessing" title="Link to this heading">¶</a></h3> <a class="reference internal" href="../library/multiprocessing.html#multiprocessing-proxy-objects">Proxy Objects</a> returned by <a class="reference internal" href="../library/multiprocessing.html#multiprocessing.Manager" title="multiprocessing.Manager"><code class="xref py py-func docutils literal notranslate">multiprocessing.Manager()</code></a> can now be nested. (Contributed by Davin Potts in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=6766">bpo-6766</a>.) </section> <section id="os"> <h3>os<a class="headerlink" href="#os" title="Link to this heading">¶</a></h3> See the summary of <a class="reference internal" href="#whatsnew36-pep519">PEP 519</a> for details on how the <a class="reference internal" href="../library/os.html#module-os" title="os: Miscellaneous operating system interfaces."><code class="xref py py-mod docutils literal notranslate">os</code></a> and <a class="reference internal" href="../library/os.path.html#module-os.path" title="os.path: Operations on pathnames."><code class="xref py py-mod docutils literal notranslate">os.path</code></a> modules now support <a class="reference internal" href="../glossary.html#term-path-like-object">path-like objects</a>. <a class="reference internal" href="../library/os.html#os.scandir" title="os.scandir"><code class="xref py py-func docutils literal notranslate">scandir()</code></a> now supports <a class="reference internal" href="../library/stdtypes.html#bytes" title="bytes"><code class="xref py py-class docutils literal notranslate">bytes</code></a> paths on Windows. A new <a class="reference internal" href="../library/os.html#os.scandir.close" title="os.scandir.close"><code class="xref py py-meth docutils literal notranslate">close()</code></a> method allows explicitly closing a <a class="reference internal" href="../library/os.html#os.scandir" title="os.scandir"><code class="xref py py-func docutils literal notranslate">scandir()</code></a> iterator. The <a class="reference internal" href="../library/os.html#os.scandir" title="os.scandir"><code class="xref py py-func docutils literal notranslate">scandir()</code></a> iterator now supports the <a class="reference internal" href="../glossary.html#term-context-manager">context manager</a> protocol. If a <code class="xref py py-func docutils literal notranslate">scandir()</code> iterator is neither exhausted nor explicitly closed a <a class="reference internal" href="../library/exceptions.html#ResourceWarning" title="ResourceWarning"><code class="xref py py-exc docutils literal notranslate">ResourceWarning</code></a> will be emitted in its destructor. (Contributed by Serhiy Storchaka in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=25994">bpo-25994</a>.) On Linux, <a class="reference internal" href="../library/os.html#os.urandom" title="os.urandom"><code class="xref py py-func docutils literal notranslate">os.urandom()</code></a> now blocks until the system urandom entropy pool is initialized to increase the security. See the <a class="pep reference external" href="https://peps.python.org/pep-0524/">PEP 524</a> for the rationale. The Linux <code class="docutils literal notranslate">getrandom()</code> syscall (get random bytes) is now exposed as the new <a class="reference internal" href="../library/os.html#os.getrandom" title="os.getrandom"><code class="xref py py-func docutils literal notranslate">os.getrandom()</code></a> function. (Contributed by Victor Stinner, part of the <a class="pep reference external" href="https://peps.python.org/pep-0524/">PEP 524</a>) </section> <section id="pathlib"> <h3>pathlib<a class="headerlink" href="#pathlib" title="Link to this heading">¶</a></h3> <a class="reference internal" href="../library/pathlib.html#module-pathlib" title="pathlib: Object-oriented filesystem paths"><code class="xref py py-mod docutils literal notranslate">pathlib</code></a> now supports <a class="reference internal" href="../glossary.html#term-path-like-object">path-like objects</a>. (Contributed by Brett Cannon in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=27186">bpo-27186</a>.) See the summary of <a class="reference internal" href="#whatsnew36-pep519">PEP 519</a> for details. </section> <section id="pdb"> <h3>pdb<a class="headerlink" href="#pdb" title="Link to this heading">¶</a></h3> The <a class="reference internal" href="../library/pdb.html#pdb.Pdb" title="pdb.Pdb"><code class="xref py py-class docutils literal notranslate">Pdb</code></a> class constructor has a new optional readrc argument to control whether <code class="docutils literal notranslate">.pdbrc</code> files should be read. </section> <section id="pickle"> <h3>pickle<a class="headerlink" href="#pickle" title="Link to this heading">¶</a></h3> Objects that need <code class="docutils literal notranslate">__new__</code> called with keyword arguments can now be pickled using <a class="reference internal" href="../library/pickle.html#pickle-protocols">pickle protocols</a> older than protocol version 4. Protocol version 4 already supports this case. (Contributed by Serhiy Storchaka in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=24164">bpo-24164</a>.) </section> <section id="pickletools"> <h3>pickletools<a class="headerlink" href="#pickletools" title="Link to this heading">¶</a></h3> <a class="reference internal" href="../library/pickletools.html#pickletools.dis" title="pickletools.dis"><code class="xref py py-func docutils literal notranslate">pickletools.dis()</code></a> now outputs the implicit memo index for the <code class="docutils literal notranslate">MEMOIZE</code> opcode. (Contributed by Serhiy Storchaka in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=25382">bpo-25382</a>.) </section> <section id="pydoc"> <h3>pydoc<a class="headerlink" href="#pydoc" title="Link to this heading">¶</a></h3> The <a class="reference internal" href="../library/pydoc.html#module-pydoc" title="pydoc: Documentation generator and online help system."><code class="xref py py-mod docutils literal notranslate">pydoc</code></a> module has learned to respect the <code class="docutils literal notranslate">MANPAGER</code> environment variable. (Contributed by Matthias Klose in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=8637">bpo-8637</a>.) <a class="reference internal" href="../library/functions.html#help" title="help"><code class="xref py py-func docutils literal notranslate">help()</code></a> and <a class="reference internal" href="../library/pydoc.html#module-pydoc" title="pydoc: Documentation generator and online help system."><code class="xref py py-mod docutils literal notranslate">pydoc</code></a> can now list named tuple fields in the order they were defined rather than alphabetically. (Contributed by Raymond Hettinger in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=24879">bpo-24879</a>.) </section> <section id="random"> <h3>random<a class="headerlink" href="#random" title="Link to this heading">¶</a></h3> The new <a class="reference internal" href="../library/random.html#random.choices" title="random.choices"><code class="xref py py-func docutils literal notranslate">choices()</code></a> function returns a list of elements of specified size from the given population with optional weights. (Contributed by Raymond Hettinger in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=18844">bpo-18844</a>.) </section> <section id="re"> <h3>re<a class="headerlink" href="#re" title="Link to this heading">¶</a></h3> Added support of modifier spans in regular expressions. Examples: <code class="docutils literal notranslate">'(?i:p)ython'</code> matches <code class="docutils literal notranslate">'python'</code> and <code class="docutils literal notranslate">'Python'</code>, but not <code class="docutils literal notranslate">'PYTHON'</code>; <code class="docutils literal notranslate">'(?i)g(?-i:v)r'</code> matches <code class="docutils literal notranslate">'GvR'</code> and <code class="docutils literal notranslate">'gvr'</code>, but not <code class="docutils literal notranslate">'GVR'</code>. (Contributed by Serhiy Storchaka in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=433028">bpo-433028</a>.) Match object groups can be accessed by <code class="docutils literal notranslate">__getitem__</code>, which is equivalent to <code class="docutils literal notranslate">group()</code>. So <code class="docutils literal notranslate">mo['name']</code> is now equivalent to <code class="docutils literal notranslate">mo.group('name')</code>. (Contributed by Eric Smith in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=24454">bpo-24454</a>.) <a class="reference internal" href="../library/re.html#re.Match" title="re.Match"><code class="xref py py-class docutils literal notranslate">Match</code></a> objects now support <a class="reference internal" href="../reference/datamodel.html#object.__index__" title="object.__index__"><code class="xref py py-meth docutils literal notranslate">index-like objects</code></a> as group indices. (Contributed by Jeroen Demeyer and Xiang Zhang in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=27177">bpo-27177</a>.) </section> <section id="readline"> <h3>readline<a class="headerlink" href="#readline" title="Link to this heading">¶</a></h3> Added <a class="reference internal" href="../library/readline.html#readline.set_auto_history" title="readline.set_auto_history"><code class="xref py py-func docutils literal notranslate">set_auto_history()</code></a> to enable or disable automatic addition of input to the history list. (Contributed by Tyler Crompton in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=26870">bpo-26870</a>.) </section> <section id="rlcompleter"> <h3>rlcompleter<a class="headerlink" href="#rlcompleter" title="Link to this heading">¶</a></h3> Private and special attribute names now are omitted unless the prefix starts with underscores. A space or a colon is added after some completed keywords. (Contributed by Serhiy Storchaka in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=25011">bpo-25011</a> and <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=25209">bpo-25209</a>.) </section> <section id="shlex"> <h3>shlex<a class="headerlink" href="#shlex" title="Link to this heading">¶</a></h3> The <a class="reference internal" href="../library/shlex.html#shlex.shlex" title="shlex.shlex"><code class="xref py py-class docutils literal notranslate">shlex</code></a> has much <a class="reference internal" href="../library/shlex.html#improved-shell-compatibility">improved shell compatibility</a> through the new punctuation_chars argument to control which characters are treated as punctuation. (Contributed by Vinay Sajip in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=1521950">bpo-1521950</a>.) </section> <section id="site"> <h3>site<a class="headerlink" href="#site" title="Link to this heading">¶</a></h3> When specifying paths to add to <a class="reference internal" href="../library/sys.html#sys.path" title="sys.path"><code class="xref py py-data docutils literal notranslate">sys.path</code></a> in a <code class="docutils literal notranslate">.pth</code> file, you may now specify file paths on top of directories (e.g. zip files). (Contributed by Wolfgang Langner in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=26587">bpo-26587</a>). </section> <section id="sqlite3"> <h3>sqlite3<a class="headerlink" href="#sqlite3" title="Link to this heading">¶</a></h3> <a class="reference internal" href="../library/sqlite3.html#sqlite3.Cursor.lastrowid" title="sqlite3.Cursor.lastrowid"><code class="xref py py-attr docutils literal notranslate">sqlite3.Cursor.lastrowid</code></a> now supports the <code class="docutils literal notranslate">REPLACE</code> statement. (Contributed by Alex LordThorsen in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=16864">bpo-16864</a>.) </section> <section id="socket"> <h3>socket<a class="headerlink" href="#socket" title="Link to this heading">¶</a></h3> The <a class="reference internal" href="../library/socket.html#socket.socket.ioctl" title="socket.socket.ioctl"><code class="xref py py-func docutils literal notranslate">ioctl()</code></a> function now supports the <a class="reference internal" href="../library/socket.html#socket.SIO_LOOPBACK_FAST_PATH" title="socket.SIO_LOOPBACK_FAST_PATH"><code class="xref py py-const docutils literal notranslate">SIO_LOOPBACK_FAST_PATH</code></a> control code. (Contributed by Daniel Stokes in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=26536">bpo-26536</a>.) The <a class="reference internal" href="../library/socket.html#socket.socket.getsockopt" title="socket.socket.getsockopt"><code class="xref py py-meth docutils literal notranslate">getsockopt()</code></a> constants <code class="docutils literal notranslate">SO_DOMAIN</code>, <code class="docutils literal notranslate">SO_PROTOCOL</code>, <code class="docutils literal notranslate">SO_PEERSEC</code>, and <code class="docutils literal notranslate">SO_PASSSEC</code> are now supported. (Contributed by Christian Heimes in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=26907">bpo-26907</a>.) The <a class="reference internal" href="../library/socket.html#socket.socket.setsockopt" title="socket.socket.setsockopt"><code class="xref py py-meth docutils literal notranslate">setsockopt()</code></a> now supports the <code class="docutils literal notranslate">setsockopt(level, optname, None, optlen: int)</code> form. (Contributed by Christian Heimes in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=27744">bpo-27744</a>.) The socket module now supports the address family <a class="reference internal" href="../library/socket.html#socket.AF_ALG" title="socket.AF_ALG"><code class="xref py py-const docutils literal notranslate">AF_ALG</code></a> to interface with Linux Kernel crypto API. <code class="docutils literal notranslate">ALG_*</code>, <code class="docutils literal notranslate">SOL_ALG</code> and <a class="reference internal" href="../library/socket.html#socket.socket.sendmsg_afalg" title="socket.socket.sendmsg_afalg"><code class="xref py py-meth docutils literal notranslate">sendmsg_afalg()</code></a> were added. (Contributed by Christian Heimes in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=27744">bpo-27744</a> with support from Victor Stinner.) New Linux constants <code class="docutils literal notranslate">TCP_USER_TIMEOUT</code> and <code class="docutils literal notranslate">TCP_CONGESTION</code> were added. (Contributed by Omar Sandoval, <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=26273">bpo-26273</a>). </section> <section id="socketserver"> <h3>socketserver<a class="headerlink" href="#socketserver" title="Link to this heading">¶</a></h3> Servers based on the <a class="reference internal" href="../library/socketserver.html#module-socketserver" title="socketserver: A framework for network servers."><code class="xref py py-mod docutils literal notranslate">socketserver</code></a> module, including those defined in <a class="reference internal" href="../library/http.server.html#module-http.server" title="http.server: HTTP server and request handlers."><code class="xref py py-mod docutils literal notranslate">http.server</code></a>, <a class="reference internal" href="../library/xmlrpc.server.html#module-xmlrpc.server" title="xmlrpc.server: Basic XML-RPC server implementations."><code class="xref py py-mod docutils literal notranslate">xmlrpc.server</code></a> and <a class="reference internal" href="../library/wsgiref.html#module-wsgiref.simple_server" title="wsgiref.simple_server: A simple WSGI HTTP server."><code class="xref py py-mod docutils literal notranslate">wsgiref.simple_server</code></a>, now support the <a class="reference internal" href="../glossary.html#term-context-manager">context manager</a> protocol. (Contributed by Aviv Palivoda in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=26404">bpo-26404</a>.) The <code class="xref py py-attr docutils literal notranslate">wfile</code> attribute of <a class="reference internal" href="../library/socketserver.html#socketserver.StreamRequestHandler" title="socketserver.StreamRequestHandler"><code class="xref py py-class docutils literal notranslate">StreamRequestHandler</code></a> classes now implements the <a class="reference internal" href="../library/io.html#io.BufferedIOBase" title="io.BufferedIOBase"><code class="xref py py-class docutils literal notranslate">io.BufferedIOBase</code></a> writable interface. In particular, calling <a class="reference internal" href="../library/io.html#io.BufferedIOBase.write" title="io.BufferedIOBase.write"><code class="xref py py-meth docutils literal notranslate">write()</code></a> is now guaranteed to send the data in full. (Contributed by Martin Panter in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=26721">bpo-26721</a>.) </section> <section id="ssl"> <h3>ssl<a class="headerlink" href="#ssl" title="Link to this heading">¶</a></h3> <a class="reference internal" href="../library/ssl.html#module-ssl" title="ssl: TLS/SSL wrapper for socket objects"><code class="xref py py-mod docutils literal notranslate">ssl</code></a> supports OpenSSL 1.1.0. The minimum recommend version is 1.0.2. (Contributed by Christian Heimes in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=26470">bpo-26470</a>.) 3DES has been removed from the default cipher suites and ChaCha20 Poly1305 cipher suites have been added. (Contributed by Christian Heimes in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=27850">bpo-27850</a> and <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=27766">bpo-27766</a>.) <a class="reference internal" href="../library/ssl.html#ssl.SSLContext" title="ssl.SSLContext"><code class="xref py py-class docutils literal notranslate">SSLContext</code></a> has better default configuration for options and ciphers. (Contributed by Christian Heimes in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=28043">bpo-28043</a>.) SSL session can be copied from one client-side connection to another with the new <a class="reference internal" href="../library/ssl.html#ssl.SSLSession" title="ssl.SSLSession"><code class="xref py py-class docutils literal notranslate">SSLSession</code></a> class. TLS session resumption can speed up the initial handshake, reduce latency and improve performance (Contributed by Christian Heimes in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=19500">bpo-19500</a> based on a draft by Alex Warhawk.) The new <a class="reference internal" href="../library/ssl.html#ssl.SSLContext.get_ciphers" title="ssl.SSLContext.get_ciphers"><code class="xref py py-meth docutils literal notranslate">get_ciphers()</code></a> method can be used to get a list of enabled ciphers in order of cipher priority. All constants and flags have been converted to <a class="reference internal" href="../library/enum.html#enum.IntEnum" title="enum.IntEnum"><code class="xref py py-class docutils literal notranslate">IntEnum</code></a> and <code class="xref py py-class docutils literal notranslate">IntFlags</code>. (Contributed by Christian Heimes in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=28025">bpo-28025</a>.) Server and client-side specific TLS protocols for <a class="reference internal" href="../library/ssl.html#ssl.SSLContext" title="ssl.SSLContext"><code class="xref py py-class docutils literal notranslate">SSLContext</code></a> were added. (Contributed by Christian Heimes in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=28085">bpo-28085</a>.) Added <a class="reference internal" href="../library/ssl.html#ssl.SSLContext.post_handshake_auth" title="ssl.SSLContext.post_handshake_auth"><code class="xref py py-attr docutils literal notranslate">ssl.SSLContext.post_handshake_auth</code></a> to enable and <a class="reference internal" href="../library/ssl.html#ssl.SSLSocket.verify_client_post_handshake" title="ssl.SSLSocket.verify_client_post_handshake"><code class="xref py py-meth docutils literal notranslate">ssl.SSLSocket.verify_client_post_handshake()</code></a> to initiate TLS 1.3 post-handshake authentication. (Contributed by Christian Heimes in <a class="reference external" href="https://github.com/python/cpython/issues/78851">gh-78851</a>.) </section> <section id="statistics"> <h3>statistics<a class="headerlink" href="#statistics" title="Link to this heading">¶</a></h3> A new <a class="reference internal" href="../library/statistics.html#statistics.harmonic_mean" title="statistics.harmonic_mean"><code class="xref py py-func docutils literal notranslate">harmonic_mean()</code></a> function has been added. (Contributed by Steven D’Aprano in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=27181">bpo-27181</a>.) </section> <section id="struct"> <h3>struct<a class="headerlink" href="#struct" title="Link to this heading">¶</a></h3> <a class="reference internal" href="../library/struct.html#module-struct" title="struct: Interpret bytes as packed binary data."><code class="xref py py-mod docutils literal notranslate">struct</code></a> now supports IEEE 754 half-precision floats via the <code class="docutils literal notranslate">'e'</code> format specifier. (Contributed by Eli Stevens, Mark Dickinson in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=11734">bpo-11734</a>.) </section> <section id="subprocess"> <h3>subprocess<a class="headerlink" href="#subprocess" title="Link to this heading">¶</a></h3> <a class="reference internal" href="../library/subprocess.html#subprocess.Popen" title="subprocess.Popen"><code class="xref py py-class docutils literal notranslate">subprocess.Popen</code></a> destructor now emits a <a class="reference internal" href="../library/exceptions.html#ResourceWarning" title="ResourceWarning"><code class="xref py py-exc docutils literal notranslate">ResourceWarning</code></a> warning if the child process is still running. Use the context manager protocol (<code class="docutils literal notranslate">with proc: ...</code>) or explicitly call the <a class="reference internal" href="../library/subprocess.html#subprocess.Popen.wait" title="subprocess.Popen.wait"><code class="xref py py-meth docutils literal notranslate">wait()</code></a> method to read the exit status of the child process. (Contributed by Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=26741">bpo-26741</a>.) The <a class="reference internal" href="../library/subprocess.html#subprocess.Popen" title="subprocess.Popen"><code class="xref py py-class docutils literal notranslate">subprocess.Popen</code></a> constructor and all functions that pass arguments through to it now accept encoding and errors arguments. Specifying either of these will enable text mode for the stdin, stdout and stderr streams. (Contributed by Steve Dower in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=6135">bpo-6135</a>.) </section> <section id="sys"> <h3>sys<a class="headerlink" href="#sys" title="Link to this heading">¶</a></h3> The new <a class="reference internal" href="../library/sys.html#sys.getfilesystemencodeerrors" title="sys.getfilesystemencodeerrors"><code class="xref py py-func docutils literal notranslate">getfilesystemencodeerrors()</code></a> function returns the name of the error mode used to convert between Unicode filenames and bytes filenames. (Contributed by Steve Dower in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=27781">bpo-27781</a>.) On Windows the return value of the <a class="reference internal" href="../library/sys.html#sys.getwindowsversion" title="sys.getwindowsversion"><code class="xref py py-func docutils literal notranslate">getwindowsversion()</code></a> function now includes the platform_version field which contains the accurate major version, minor version and build number of the current operating system, rather than the version that is being emulated for the process (Contributed by Steve Dower in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=27932">bpo-27932</a>.) </section> <section id="telnetlib"> <h3>telnetlib<a class="headerlink" href="#telnetlib" title="Link to this heading">¶</a></h3> <code class="xref py py-class docutils literal notranslate">telnetlib.Telnet</code> is now a context manager (contributed by Stéphane Wirtel in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=25485">bpo-25485</a>). </section> <section id="time"> <h3>time<a class="headerlink" href="#time" title="Link to this heading">¶</a></h3> The <a class="reference internal" href="../library/time.html#time.struct_time" title="time.struct_time"><code class="xref py py-class docutils literal notranslate">struct_time</code></a> attributes <code class="xref py py-attr docutils literal notranslate">tm_gmtoff</code> and <code class="xref py py-attr docutils literal notranslate">tm_zone</code> are now available on all platforms. </section> <section id="timeit"> <h3>timeit<a class="headerlink" href="#timeit" title="Link to this heading">¶</a></h3> The new <a class="reference internal" href="../library/timeit.html#timeit.Timer.autorange" title="timeit.Timer.autorange"><code class="xref py py-meth docutils literal notranslate">Timer.autorange()</code></a> convenience method has been added to call <a class="reference internal" href="../library/timeit.html#timeit.Timer.timeit" title="timeit.Timer.timeit"><code class="xref py py-meth docutils literal notranslate">Timer.timeit()</code></a> repeatedly so that the total run time is greater or equal to 200 milliseconds. (Contributed by Steven D’Aprano in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=6422">bpo-6422</a>.) <a class="reference internal" href="../library/timeit.html#module-timeit" title="timeit: Measure the execution time of small code snippets."><code class="xref py py-mod docutils literal notranslate">timeit</code></a> now warns when there is substantial (4x) variance between best and worst times. (Contributed by Serhiy Storchaka in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=23552">bpo-23552</a>.) </section> <section id="tkinter"> <h3>tkinter<a class="headerlink" href="#tkinter" title="Link to this heading">¶</a></h3> Added methods <code class="xref py py-meth docutils literal notranslate">trace_add()</code>, <code class="xref py py-meth docutils literal notranslate">trace_remove()</code> and <code class="xref py py-meth docutils literal notranslate">trace_info()</code> in the <code class="xref py py-class docutils literal notranslate">tkinter.Variable</code> class. They replace old methods <code class="xref py py-meth docutils literal notranslate">trace_variable()</code>, <code class="xref py py-meth docutils literal notranslate">trace()</code>, <code class="xref py py-meth docutils literal notranslate">trace_vdelete()</code> and <code class="xref py py-meth docutils literal notranslate">trace_vinfo()</code> that use obsolete Tcl commands and might not work in future versions of Tcl. (Contributed by Serhiy Storchaka in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=22115">bpo-22115</a>). </section> <section id="traceback"> <h3>traceback<a class="headerlink" href="#traceback" title="Link to this heading">¶</a></h3> Both the traceback module and the interpreter’s builtin exception display now abbreviate long sequences of repeated lines in tracebacks as shown in the following example: <div class="highlight-python3 notranslate"><div class="highlight"><pre>>>> def f(): f() ... >>> f() Traceback (most recent call last): File "<stdin>", line 1, in <module> File "<stdin>", line 1, in f File "<stdin>", line 1, in f File "<stdin>", line 1, in f [Previous line repeated 995 more times] RecursionError: maximum recursion depth exceeded </pre></div> </div> (Contributed by Emanuel Barry in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=26823">bpo-26823</a>.) </section> <section id="tracemalloc"> <h3>tracemalloc<a class="headerlink" href="#tracemalloc" title="Link to this heading">¶</a></h3> The <a class="reference internal" href="../library/tracemalloc.html#module-tracemalloc" title="tracemalloc: Trace memory allocations."><code class="xref py py-mod docutils literal notranslate">tracemalloc</code></a> module now supports tracing memory allocations in multiple different address spaces. The new <a class="reference internal" href="../library/tracemalloc.html#tracemalloc.DomainFilter" title="tracemalloc.DomainFilter"><code class="xref py py-class docutils literal notranslate">DomainFilter</code></a> filter class has been added to filter block traces by their address space (domain). (Contributed by Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=26588">bpo-26588</a>.) </section> <section id="typing"> <h3>typing<a class="headerlink" href="#typing" title="Link to this heading">¶</a></h3> Since the <a class="reference internal" href="../library/typing.html#module-typing" title="typing: Support for type hints (see :pep:`484`)."><code class="xref py py-mod docutils literal notranslate">typing</code></a> module is <a class="reference internal" href="../glossary.html#term-provisional-API">provisional</a>, all changes introduced in Python 3.6 have also been backported to Python 3.5.x. The <a class="reference internal" href="../library/typing.html#module-typing" title="typing: Support for type hints (see :pep:`484`)."><code class="xref py py-mod docutils literal notranslate">typing</code></a> module has a much improved support for generic type aliases. For example <code class="docutils literal notranslate">Dict[str, Tuple[S, T]]</code> is now a valid type annotation. (Contributed by Guido van Rossum in <a class="reference external" href="https://github.com/python/typing/pull/195">Github #195</a>.) The <a class="reference internal" href="../library/typing.html#typing.ContextManager" title="typing.ContextManager"><code class="xref py py-class docutils literal notranslate">typing.ContextManager</code></a> class has been added for representing <a class="reference internal" href="../library/contextlib.html#contextlib.AbstractContextManager" title="contextlib.AbstractContextManager"><code class="xref py py-class docutils literal notranslate">contextlib.AbstractContextManager</code></a>. (Contributed by Brett Cannon in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=25609">bpo-25609</a>.) The <a class="reference internal" href="../library/typing.html#typing.Collection" title="typing.Collection"><code class="xref py py-class docutils literal notranslate">typing.Collection</code></a> class has been added for representing <a class="reference internal" href="../library/collections.abc.html#collections.abc.Collection" title="collections.abc.Collection"><code class="xref py py-class docutils literal notranslate">collections.abc.Collection</code></a>. (Contributed by Ivan Levkivskyi in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=27598">bpo-27598</a>.) The <a class="reference internal" href="../library/typing.html#typing.ClassVar" title="typing.ClassVar"><code class="xref py py-const docutils literal notranslate">typing.ClassVar</code></a> type construct has been added to mark class variables. As introduced in <a class="pep reference external" href="https://peps.python.org/pep-0526/">PEP 526</a>, a variable annotation wrapped in ClassVar indicates that a given attribute is intended to be used as a class variable and should not be set on instances of that class. (Contributed by Ivan Levkivskyi in <a class="reference external" href="https://github.com/python/typing/pull/280">Github #280</a>.) A new <a class="reference internal" href="../library/typing.html#typing.TYPE_CHECKING" title="typing.TYPE_CHECKING"><code class="xref py py-const docutils literal notranslate">TYPE_CHECKING</code></a> constant that is assumed to be <code class="docutils literal notranslate">True</code> by the static type checkers, but is <code class="docutils literal notranslate">False</code> at runtime. (Contributed by Guido van Rossum in <a class="reference external" href="https://github.com/python/typing/issues/230">Github #230</a>.) A new <a class="reference internal" href="../library/typing.html#typing.NewType" title="typing.NewType"><code class="xref py py-func docutils literal notranslate">NewType()</code></a> helper function has been added to create lightweight distinct types for annotations: <div class="highlight-python3 notranslate"><div class="highlight"><pre>from typing import NewType UserId = NewType('UserId', int) some_id = UserId(524313) </pre></div> </div> The static type checker will treat the new type as if it were a subclass of the original type. (Contributed by Ivan Levkivskyi in <a class="reference external" href="https://github.com/python/typing/issues/189">Github #189</a>.) </section> <section id="unicodedata"> <h3>unicodedata<a class="headerlink" href="#unicodedata" title="Link to this heading">¶</a></h3> The <a class="reference internal" href="../library/unicodedata.html#module-unicodedata" title="unicodedata: Access the Unicode Database."><code class="xref py py-mod docutils literal notranslate">unicodedata</code></a> module now uses data from <a class="reference external" href="https://unicode.org/versions/Unicode9.0.0/">Unicode 9.0.0</a>. (Contributed by Benjamin Peterson.) </section> <section id="unittest-mock"> <h3>unittest.mock<a class="headerlink" href="#unittest-mock" title="Link to this heading">¶</a></h3> The <a class="reference internal" href="../library/unittest.mock.html#unittest.mock.Mock" title="unittest.mock.Mock"><code class="xref py py-class docutils literal notranslate">Mock</code></a> class has the following improvements: <ul class="simple"> <li>Two new methods, <a class="reference internal" href="../library/unittest.mock.html#unittest.mock.Mock.assert_called" title="unittest.mock.Mock.assert_called"><code class="xref py py-meth docutils literal notranslate">Mock.assert_called()</code></a> and <a class="reference internal" href="../library/unittest.mock.html#unittest.mock.Mock.assert_called_once" title="unittest.mock.Mock.assert_called_once"><code class="xref py py-meth docutils literal notranslate">Mock.assert_called_once()</code></a> to check if the mock object was called. (Contributed by Amit Saha in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=26323">bpo-26323</a>.)</li> <li>The <a class="reference internal" href="../library/unittest.mock.html#unittest.mock.Mock.reset_mock" title="unittest.mock.Mock.reset_mock"><code class="xref py py-meth docutils literal notranslate">Mock.reset_mock()</code></a> method now has two optional keyword only arguments: return_value and side_effect. (Contributed by Kushal Das in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=21271">bpo-21271</a>.)</li> </ul> </section> <section id="urllib-request"> <h3>urllib.request<a class="headerlink" href="#urllib-request" title="Link to this heading">¶</a></h3> If a HTTP request has a file or iterable body (other than a bytes object) but no <code class="docutils literal notranslate">Content-Length</code> header, rather than throwing an error, <code class="xref py py-class docutils literal notranslate">AbstractHTTPHandler</code> now falls back to use chunked transfer encoding. (Contributed by Demian Brecht and Rolf Krahl in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=12319">bpo-12319</a>.) </section> <section id="urllib-robotparser"> <h3>urllib.robotparser<a class="headerlink" href="#urllib-robotparser" title="Link to this heading">¶</a></h3> <a class="reference internal" href="../library/urllib.robotparser.html#urllib.robotparser.RobotFileParser" title="urllib.robotparser.RobotFileParser"><code class="xref py py-class docutils literal notranslate">RobotFileParser</code></a> now supports the <code class="docutils literal notranslate">Crawl-delay</code> and <code class="docutils literal notranslate">Request-rate</code> extensions. (Contributed by Nikolay Bogoychev in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=16099">bpo-16099</a>.) </section> <section id="venv"> <h3>venv<a class="headerlink" href="#venv" title="Link to this heading">¶</a></h3> <a class="reference internal" href="../library/venv.html#module-venv" title="venv: Creation of virtual environments."><code class="xref py py-mod docutils literal notranslate">venv</code></a> accepts a new parameter <code class="docutils literal notranslate">--prompt</code>. This parameter provides an alternative prefix for the virtual environment. (Proposed by Łukasz Balcerzak and ported to 3.6 by Stéphane Wirtel in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=22829">bpo-22829</a>.) </section> <section id="warnings"> <h3>warnings<a class="headerlink" href="#warnings" title="Link to this heading">¶</a></h3> A new optional source parameter has been added to the <a class="reference internal" href="../library/warnings.html#warnings.warn_explicit" title="warnings.warn_explicit"><code class="xref py py-func docutils literal notranslate">warnings.warn_explicit()</code></a> function: the destroyed object which emitted a <a class="reference internal" href="../library/exceptions.html#ResourceWarning" title="ResourceWarning"><code class="xref py py-exc docutils literal notranslate">ResourceWarning</code></a>. A source attribute has also been added to <code class="xref py py-class docutils literal notranslate">warnings.WarningMessage</code> (contributed by Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=26568">bpo-26568</a> and <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=26567">bpo-26567</a>). When a <a class="reference internal" href="../library/exceptions.html#ResourceWarning" title="ResourceWarning"><code class="xref py py-exc docutils literal notranslate">ResourceWarning</code></a> warning is logged, the <a class="reference internal" href="../library/tracemalloc.html#module-tracemalloc" title="tracemalloc: Trace memory allocations."><code class="xref py py-mod docutils literal notranslate">tracemalloc</code></a> module is now used to try to retrieve the traceback where the destroyed object was allocated. Example with the script <code class="docutils literal notranslate">example.py</code>: <div class="highlight-python3 notranslate"><div class="highlight"><pre>import warnings def func(): return open(__file__) f = func() f = None </pre></div> </div> Output of the command <code class="docutils literal notranslate">python3.6 -Wd -X tracemalloc=5 example.py</code>: <div class="highlight-python3 notranslate"><div class="highlight"><pre>example.py:7: ResourceWarning: unclosed file <_io.TextIOWrapper name='example.py' mode='r' encoding='UTF-8'> f = None Object allocated at (most recent call first): File "example.py", lineno 4 return open(__file__) File "example.py", lineno 6 f = func() </pre></div> </div> The “Object allocated at” traceback is new and is only displayed if <a class="reference internal" href="../library/tracemalloc.html#module-tracemalloc" title="tracemalloc: Trace memory allocations."><code class="xref py py-mod docutils literal notranslate">tracemalloc</code></a> is tracing Python memory allocations and if the <a class="reference internal" href="../library/warnings.html#module-warnings" title="warnings: Issue warning messages and control their disposition."><code class="xref py py-mod docutils literal notranslate">warnings</code></a> module was already imported. </section> <section id="winreg"> <h3>winreg<a class="headerlink" href="#winreg" title="Link to this heading">¶</a></h3> Added the 64-bit integer type <a class="reference internal" href="../library/winreg.html#winreg.REG_QWORD" title="winreg.REG_QWORD"><code class="xref py py-data docutils literal notranslate">REG_QWORD</code></a>. (Contributed by Clement Rouault in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=23026">bpo-23026</a>.) </section> <section id="winsound"> <h3>winsound<a class="headerlink" href="#winsound" title="Link to this heading">¶</a></h3> Allowed keyword arguments to be passed to <a class="reference internal" href="../library/winsound.html#winsound.Beep" title="winsound.Beep"><code class="xref py py-func docutils literal notranslate">Beep</code></a>, <a class="reference internal" href="../library/winsound.html#winsound.MessageBeep" title="winsound.MessageBeep"><code class="xref py py-func docutils literal notranslate">MessageBeep</code></a>, and <a class="reference internal" href="../library/winsound.html#winsound.PlaySound" title="winsound.PlaySound"><code class="xref py py-func docutils literal notranslate">PlaySound</code></a> (<a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=27982">bpo-27982</a>). </section> <section id="xmlrpc-client"> <h3>xmlrpc.client<a class="headerlink" href="#xmlrpc-client" title="Link to this heading">¶</a></h3> The <a class="reference internal" href="../library/xmlrpc.client.html#module-xmlrpc.client" title="xmlrpc.client: XML-RPC client access."><code class="xref py py-mod docutils literal notranslate">xmlrpc.client</code></a> module now supports unmarshalling additional data types used by the Apache XML-RPC implementation for numerics and <code class="docutils literal notranslate">None</code>. (Contributed by Serhiy Storchaka in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=26885">bpo-26885</a>.) </section> <section id="zipfile"> <h3>zipfile<a class="headerlink" href="#zipfile" title="Link to this heading">¶</a></h3> A new <a class="reference internal" href="../library/zipfile.html#zipfile.ZipInfo.from_file" title="zipfile.ZipInfo.from_file"><code class="xref py py-meth docutils literal notranslate">ZipInfo.from_file()</code></a> class method allows making a <a class="reference internal" href="../library/zipfile.html#zipfile.ZipInfo" title="zipfile.ZipInfo"><code class="xref py py-class docutils literal notranslate">ZipInfo</code></a> instance from a filesystem file. A new <a class="reference internal" href="../library/zipfile.html#zipfile.ZipInfo.is_dir" title="zipfile.ZipInfo.is_dir"><code class="xref py py-meth docutils literal notranslate">ZipInfo.is_dir()</code></a> method can be used to check if the <a class="reference internal" href="../library/zipfile.html#zipfile.ZipInfo" title="zipfile.ZipInfo"><code class="xref py py-class docutils literal notranslate">ZipInfo</code></a> instance represents a directory. (Contributed by Thomas Kluyver in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=26039">bpo-26039</a>.) The <a class="reference internal" href="../library/zipfile.html#zipfile.ZipFile.open" title="zipfile.ZipFile.open"><code class="xref py py-meth docutils literal notranslate">ZipFile.open()</code></a> method can now be used to write data into a ZIP file, as well as for extracting data. (Contributed by Thomas Kluyver in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=26039">bpo-26039</a>.) </section> <section id="zlib"> <h3>zlib<a class="headerlink" href="#zlib" title="Link to this heading">¶</a></h3> The <a class="reference internal" href="../library/zlib.html#zlib.compress" title="zlib.compress"><code class="xref py py-func docutils literal notranslate">compress()</code></a> and <a class="reference internal" href="../library/zlib.html#zlib.decompress" title="zlib.decompress"><code class="xref py py-func docutils literal notranslate">decompress()</code></a> functions now accept keyword arguments. (Contributed by Aviv Palivoda in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=26243">bpo-26243</a> and Xiang Zhang in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=16764">bpo-16764</a> respectively.) </section> </section> <section id="optimizations"> <h2>Optimizations<a class="headerlink" href="#optimizations" title="Link to this heading">¶</a></h2> <ul class="simple"> <li>The Python interpreter now uses a 16-bit wordcode instead of bytecode which made a number of opcode optimizations possible. (Contributed by Demur Rumed with input and reviews from Serhiy Storchaka and Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=26647">bpo-26647</a> and <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=28050">bpo-28050</a>.)</li> <li>The <a class="reference internal" href="../library/asyncio-future.html#asyncio.Future" title="asyncio.Future"><code class="xref py py-class docutils literal notranslate">asyncio.Future</code></a> class now has an optimized C implementation. (Contributed by Yury Selivanov and INADA Naoki in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=26081">bpo-26081</a>.)</li> <li>The <a class="reference internal" href="../library/asyncio-task.html#asyncio.Task" title="asyncio.Task"><code class="xref py py-class docutils literal notranslate">asyncio.Task</code></a> class now has an optimized C implementation. (Contributed by Yury Selivanov in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=28544">bpo-28544</a>.)</li> <li>Various implementation improvements in the <a class="reference internal" href="../library/typing.html#module-typing" title="typing: Support for type hints (see :pep:`484`)."><code class="xref py py-mod docutils literal notranslate">typing</code></a> module (such as caching of generic types) allow up to 30 times performance improvements and reduced memory footprint.</li> <li>The ASCII decoder is now up to 60 times as fast for error handlers <code class="docutils literal notranslate">surrogateescape</code>, <code class="docutils literal notranslate">ignore</code> and <code class="docutils literal notranslate">replace</code> (Contributed by Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=24870">bpo-24870</a>).</li> <li>The ASCII and the Latin1 encoders are now up to 3 times as fast for the error handler <code class="docutils literal notranslate">surrogateescape</code> (Contributed by Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=25227">bpo-25227</a>).</li> <li>The UTF-8 encoder is now up to 75 times as fast for error handlers <code class="docutils literal notranslate">ignore</code>, <code class="docutils literal notranslate">replace</code>, <code class="docutils literal notranslate">surrogateescape</code>, <code class="docutils literal notranslate">surrogatepass</code> (Contributed by Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=25267">bpo-25267</a>).</li> <li>The UTF-8 decoder is now up to 15 times as fast for error handlers <code class="docutils literal notranslate">ignore</code>, <code class="docutils literal notranslate">replace</code> and <code class="docutils literal notranslate">surrogateescape</code> (Contributed by Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=25301">bpo-25301</a>).</li> <li><code class="docutils literal notranslate">bytes % args</code> is now up to 2 times faster. (Contributed by Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=25349">bpo-25349</a>).</li> <li><code class="docutils literal notranslate">bytearray % args</code> is now between 2.5 and 5 times faster. (Contributed by Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=25399">bpo-25399</a>).</li> <li>Optimize <a class="reference internal" href="../library/stdtypes.html#bytes.fromhex" title="bytes.fromhex"><code class="xref py py-meth docutils literal notranslate">bytes.fromhex()</code></a> and <a class="reference internal" href="../library/stdtypes.html#bytearray.fromhex" title="bytearray.fromhex"><code class="xref py py-meth docutils literal notranslate">bytearray.fromhex()</code></a>: they are now between 2x and 3.5x faster. (Contributed by Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=25401">bpo-25401</a>).</li> <li>Optimize <code class="docutils literal notranslate">bytes.replace(b'', b'.')</code> and <code class="docutils literal notranslate">bytearray.replace(b'', b'.')</code>: up to 80% faster. (Contributed by Josh Snider in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=26574">bpo-26574</a>).</li> <li>Allocator functions of the <a class="reference internal" href="../c-api/memory.html#c.PyMem_Malloc" title="PyMem_Malloc"><code class="xref c c-func docutils literal notranslate">PyMem_Malloc()</code></a> domain (<a class="reference internal" href="../c-api/memory.html#c.PYMEM_DOMAIN_MEM" title="PYMEM_DOMAIN_MEM"><code class="xref c c-macro docutils literal notranslate">PYMEM_DOMAIN_MEM</code></a>) now use the <a class="reference internal" href="../c-api/memory.html#pymalloc">pymalloc memory allocator</a> instead of <code class="xref c c-func docutils literal notranslate">malloc()</code> function of the C library. The pymalloc allocator is optimized for objects smaller or equal to 512 bytes with a short lifetime, and use <code class="xref c c-func docutils literal notranslate">malloc()</code> for larger memory blocks. (Contributed by Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=26249">bpo-26249</a>).</li> <li><a class="reference internal" href="../library/pickle.html#pickle.load" title="pickle.load"><code class="xref py py-func docutils literal notranslate">pickle.load()</code></a> and <a class="reference internal" href="../library/pickle.html#pickle.loads" title="pickle.loads"><code class="xref py py-func docutils literal notranslate">pickle.loads()</code></a> are now up to 10% faster when deserializing many small objects (Contributed by Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=27056">bpo-27056</a>).</li> <li>Passing <a class="reference internal" href="../glossary.html#term-keyword-argument">keyword arguments</a> to a function has an overhead in comparison with passing <a class="reference internal" href="../glossary.html#term-positional-argument">positional arguments</a>. Now in extension functions implemented with using Argument Clinic this overhead is significantly decreased. (Contributed by Serhiy Storchaka in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=27574">bpo-27574</a>).</li> <li>Optimized <a class="reference internal" href="../library/glob.html#glob.glob" title="glob.glob"><code class="xref py py-func docutils literal notranslate">glob()</code></a> and <a class="reference internal" href="../library/glob.html#glob.iglob" title="glob.iglob"><code class="xref py py-func docutils literal notranslate">iglob()</code></a> functions in the <a class="reference internal" href="../library/glob.html#module-glob" title="glob: Unix shell style pathname pattern expansion."><code class="xref py py-mod docutils literal notranslate">glob</code></a> module; they are now about 3–6 times faster. (Contributed by Serhiy Storchaka in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=25596">bpo-25596</a>).</li> <li>Optimized globbing in <a class="reference internal" href="../library/pathlib.html#module-pathlib" title="pathlib: Object-oriented filesystem paths"><code class="xref py py-mod docutils literal notranslate">pathlib</code></a> by using <a class="reference internal" href="../library/os.html#os.scandir" title="os.scandir"><code class="xref py py-func docutils literal notranslate">os.scandir()</code></a>; it is now about 1.5–4 times faster. (Contributed by Serhiy Storchaka in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=26032">bpo-26032</a>).</li> <li><a class="reference internal" href="../library/xml.etree.elementtree.html#module-xml.etree.ElementTree" title="xml.etree.ElementTree: Implementation of the ElementTree API."><code class="xref py py-class docutils literal notranslate">xml.etree.ElementTree</code></a> parsing, iteration and deepcopy performance has been significantly improved. (Contributed by Serhiy Storchaka in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=25638">bpo-25638</a>, <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=25873">bpo-25873</a>, and <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=25869">bpo-25869</a>.)</li> <li>Creation of <a class="reference internal" href="../library/fractions.html#fractions.Fraction" title="fractions.Fraction"><code class="xref py py-class docutils literal notranslate">fractions.Fraction</code></a> instances from floats and decimals is now 2 to 3 times faster. (Contributed by Serhiy Storchaka in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=25971">bpo-25971</a>.)</li> </ul> </section> <section id="build-and-c-api-changes"> <h2>Build and C API Changes<a class="headerlink" href="#build-and-c-api-changes" title="Link to this heading">¶</a></h2> <ul class="simple"> <li>Python now requires some C99 support in the toolchain to build. Most notably, Python now uses standard integer types and macros in place of custom macros like <code class="docutils literal notranslate">PY_LONG_LONG</code>. For more information, see <a class="pep reference external" href="https://peps.python.org/pep-0007/">PEP 7</a> and <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=17884">bpo-17884</a>.</li> <li>Cross-compiling CPython with the Android NDK and the Android API level set to 21 (Android 5.0 Lollipop) or greater runs successfully. While Android is not yet a supported platform, the Python test suite runs on the Android emulator with only about 16 tests failures. See the Android meta-issue <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=26865">bpo-26865</a>.</li> <li>The <code class="docutils literal notranslate">--enable-optimizations</code> configure flag has been added. Turning it on will activate expensive optimizations like PGO. (Original patch by Alecsandru Patrascu of Intel in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=26359">bpo-26359</a>.)</li> <li>The <a class="reference internal" href="../glossary.html#term-global-interpreter-lock">GIL</a> must now be held when allocator functions of <a class="reference internal" href="../c-api/memory.html#c.PYMEM_DOMAIN_OBJ" title="PYMEM_DOMAIN_OBJ"><code class="xref c c-macro docutils literal notranslate">PYMEM_DOMAIN_OBJ</code></a> (ex: <a class="reference internal" href="../c-api/memory.html#c.PyObject_Malloc" title="PyObject_Malloc"><code class="xref c c-func docutils literal notranslate">PyObject_Malloc()</code></a>) and <a class="reference internal" href="../c-api/memory.html#c.PYMEM_DOMAIN_MEM" title="PYMEM_DOMAIN_MEM"><code class="xref c c-macro docutils literal notranslate">PYMEM_DOMAIN_MEM</code></a> (ex: <a class="reference internal" href="../c-api/memory.html#c.PyMem_Malloc" title="PyMem_Malloc"><code class="xref c c-func docutils literal notranslate">PyMem_Malloc()</code></a>) domains are called.</li> <li>New <a class="reference internal" href="../c-api/init.html#c.Py_FinalizeEx" title="Py_FinalizeEx"><code class="xref c c-func docutils literal notranslate">Py_FinalizeEx()</code></a> API which indicates if flushing buffered data failed. (Contributed by Martin Panter in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=5319">bpo-5319</a>.)</li> <li><a class="reference internal" href="../c-api/arg.html#c.PyArg_ParseTupleAndKeywords" title="PyArg_ParseTupleAndKeywords"><code class="xref c c-func docutils literal notranslate">PyArg_ParseTupleAndKeywords()</code></a> now supports <a class="reference internal" href="../glossary.html#positional-only-parameter">positional-only parameters</a>. Positional-only parameters are defined by empty names. (Contributed by Serhiy Storchaka in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=26282">bpo-26282</a>).</li> <li><code class="docutils literal notranslate">PyTraceback_Print</code> method now abbreviates long sequences of repeated lines as <code class="docutils literal notranslate">"[Previous line repeated {count} more times]"</code>. (Contributed by Emanuel Barry in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=26823">bpo-26823</a>.)</li> <li>The new <a class="reference internal" href="../c-api/exceptions.html#c.PyErr_SetImportErrorSubclass" title="PyErr_SetImportErrorSubclass"><code class="xref c c-func docutils literal notranslate">PyErr_SetImportErrorSubclass()</code></a> function allows for specifying a subclass of <a class="reference internal" href="../library/exceptions.html#ImportError" title="ImportError"><code class="xref py py-exc docutils literal notranslate">ImportError</code></a> to raise. (Contributed by Eric Snow in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=15767">bpo-15767</a>.)</li> <li>The new <a class="reference internal" href="../c-api/exceptions.html#c.PyErr_ResourceWarning" title="PyErr_ResourceWarning"><code class="xref c c-func docutils literal notranslate">PyErr_ResourceWarning()</code></a> function can be used to generate a <a class="reference internal" href="../library/exceptions.html#ResourceWarning" title="ResourceWarning"><code class="xref py py-exc docutils literal notranslate">ResourceWarning</code></a> providing the source of the resource allocation. (Contributed by Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=26567">bpo-26567</a>.)</li> <li>The new <a class="reference internal" href="../c-api/sys.html#c.PyOS_FSPath" title="PyOS_FSPath"><code class="xref c c-func docutils literal notranslate">PyOS_FSPath()</code></a> function returns the file system representation of a <a class="reference internal" href="../glossary.html#term-path-like-object">path-like object</a>. (Contributed by Brett Cannon in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=27186">bpo-27186</a>.)</li> <li>The <a class="reference internal" href="../c-api/unicode.html#c.PyUnicode_FSConverter" title="PyUnicode_FSConverter"><code class="xref c c-func docutils literal notranslate">PyUnicode_FSConverter()</code></a> and <a class="reference internal" href="../c-api/unicode.html#c.PyUnicode_FSDecoder" title="PyUnicode_FSDecoder"><code class="xref c c-func docutils literal notranslate">PyUnicode_FSDecoder()</code></a> functions will now accept <a class="reference internal" href="../glossary.html#term-path-like-object">path-like objects</a>.</li> </ul> </section> <section id="other-improvements"> <h2>Other Improvements<a class="headerlink" href="#other-improvements" title="Link to this heading">¶</a></h2> <ul> <li>When <a class="reference internal" href="../using/cmdline.html#cmdoption-version"><code class="xref std std-option docutils literal notranslate">--version</code></a> (short form: <a class="reference internal" href="../using/cmdline.html#cmdoption-V"><code class="xref std std-option docutils literal notranslate">-V</code></a>) is supplied twice, Python prints <a class="reference internal" href="../library/sys.html#sys.version" title="sys.version"><code class="xref py py-data docutils literal notranslate">sys.version</code></a> for detailed information. <div class="highlight-shell-session notranslate"><div class="highlight"><pre>$ ./python -VV Python 3.6.0b4+ (3.6:223967b49e49+, Nov 21 2016, 20:55:04) [GCC 4.2.1 Compatible Apple LLVM 8.0.0 (clang-800.0.42.1)] </pre></div> </div> </li> </ul> </section> <section id="deprecated"> <h2>Deprecated<a class="headerlink" href="#deprecated" title="Link to this heading">¶</a></h2> <section id="new-keywords"> <h3>New Keywords<a class="headerlink" href="#new-keywords" title="Link to this heading">¶</a></h3> <code class="docutils literal notranslate">async</code> and <code class="docutils literal notranslate">await</code> are not recommended to be used as variable, class, function or module names. Introduced by <a class="pep reference external" href="https://peps.python.org/pep-0492/">PEP 492</a> in Python 3.5, they will become proper keywords in Python 3.7. Starting in Python 3.6, the use of <code class="docutils literal notranslate">async</code> or <code class="docutils literal notranslate">await</code> as names will generate a <a class="reference internal" href="../library/exceptions.html#DeprecationWarning" title="DeprecationWarning"><code class="xref py py-exc docutils literal notranslate">DeprecationWarning</code></a>. </section> <section id="deprecated-python-behavior"> <h3>Deprecated Python behavior<a class="headerlink" href="#deprecated-python-behavior" title="Link to this heading">¶</a></h3> Raising the <a class="reference internal" href="../library/exceptions.html#StopIteration" title="StopIteration"><code class="xref py py-exc docutils literal notranslate">StopIteration</code></a> exception inside a generator will now generate a <a class="reference internal" href="../library/exceptions.html#DeprecationWarning" title="DeprecationWarning"><code class="xref py py-exc docutils literal notranslate">DeprecationWarning</code></a>, and will trigger a <a class="reference internal" href="../library/exceptions.html#RuntimeError" title="RuntimeError"><code class="xref py py-exc docutils literal notranslate">RuntimeError</code></a> in Python 3.7. See <a class="reference internal" href="3.5.html#whatsnew-pep-479">PEP 479: Change StopIteration handling inside generators</a> for details. The <code class="xref py py-meth docutils literal notranslate">__aiter__()</code> method is now expected to return an asynchronous iterator directly instead of returning an awaitable as previously. Doing the former will trigger a <a class="reference internal" href="../library/exceptions.html#DeprecationWarning" title="DeprecationWarning"><code class="xref py py-exc docutils literal notranslate">DeprecationWarning</code></a>. Backward compatibility will be removed in Python 3.7. (Contributed by Yury Selivanov in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=27243">bpo-27243</a>.) A backslash-character pair that is not a valid escape sequence now generates a <a class="reference internal" href="../library/exceptions.html#DeprecationWarning" title="DeprecationWarning"><code class="xref py py-exc docutils literal notranslate">DeprecationWarning</code></a>. Although this will eventually become a <a class="reference internal" href="../library/exceptions.html#SyntaxError" title="SyntaxError"><code class="xref py py-exc docutils literal notranslate">SyntaxError</code></a>, that will not be for several Python releases. (Contributed by Emanuel Barry in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=27364">bpo-27364</a>.) When performing a relative import, falling back on <code class="docutils literal notranslate">__name__</code> and <code class="docutils literal notranslate">__path__</code> from the calling module when <code class="docutils literal notranslate">__spec__</code> or <code class="docutils literal notranslate">__package__</code> are not defined now raises an <a class="reference internal" href="../library/exceptions.html#ImportWarning" title="ImportWarning"><code class="xref py py-exc docutils literal notranslate">ImportWarning</code></a>. (Contributed by Rose Ames in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=25791">bpo-25791</a>.) </section> <section id="deprecated-python-modules-functions-and-methods"> <h3>Deprecated Python modules, functions and methods<a class="headerlink" href="#deprecated-python-modules-functions-and-methods" title="Link to this heading">¶</a></h3> <section id="asynchat"> <h4>asynchat<a class="headerlink" href="#asynchat" title="Link to this heading">¶</a></h4> The <code class="xref py py-mod docutils literal notranslate">asynchat</code> has been deprecated in favor of <a class="reference internal" href="../library/asyncio.html#module-asyncio" title="asyncio: Asynchronous I/O."><code class="xref py py-mod docutils literal notranslate">asyncio</code></a>. (Contributed by Mariatta in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=25002">bpo-25002</a>.) </section> <section id="asyncore"> <h4>asyncore<a class="headerlink" href="#asyncore" title="Link to this heading">¶</a></h4> The <code class="xref py py-mod docutils literal notranslate">asyncore</code> has been deprecated in favor of <a class="reference internal" href="../library/asyncio.html#module-asyncio" title="asyncio: Asynchronous I/O."><code class="xref py py-mod docutils literal notranslate">asyncio</code></a>. (Contributed by Mariatta in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=25002">bpo-25002</a>.) </section> <section id="dbm"> <h4>dbm<a class="headerlink" href="#dbm" title="Link to this heading">¶</a></h4> Unlike other <a class="reference internal" href="../library/dbm.html#module-dbm" title="dbm: Interfaces to various Unix "database" formats."><code class="xref py py-mod docutils literal notranslate">dbm</code></a> implementations, the <a class="reference internal" href="../library/dbm.html#module-dbm.dumb" title="dbm.dumb: Portable implementation of the simple DBM interface."><code class="xref py py-mod docutils literal notranslate">dbm.dumb</code></a> module creates databases with the <code class="docutils literal notranslate">'rw'</code> mode and allows modifying the database opened with the <code class="docutils literal notranslate">'r'</code> mode. This behavior is now deprecated and will be removed in 3.8. (Contributed by Serhiy Storchaka in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=21708">bpo-21708</a>.) </section> <section id="id2"> <h4>distutils<a class="headerlink" href="#id2" title="Link to this heading">¶</a></h4> The undocumented <code class="docutils literal notranslate">extra_path</code> argument to the <code class="docutils literal notranslate">distutils.Distribution</code> constructor is now considered deprecated and will raise a warning if set. Support for this parameter will be removed in a future Python release. See <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=27919">bpo-27919</a> for details. </section> <section id="grp"> <h4>grp<a class="headerlink" href="#grp" title="Link to this heading">¶</a></h4> The support of non-integer arguments in <a class="reference internal" href="../library/grp.html#grp.getgrgid" title="grp.getgrgid"><code class="xref py py-func docutils literal notranslate">getgrgid()</code></a> has been deprecated. (Contributed by Serhiy Storchaka in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=26129">bpo-26129</a>.) </section> <section id="id3"> <h4>importlib<a class="headerlink" href="#id3" title="Link to this heading">¶</a></h4> The <a class="reference internal" href="../library/importlib.html#importlib.machinery.SourceFileLoader.load_module" title="importlib.machinery.SourceFileLoader.load_module"><code class="xref py py-meth docutils literal notranslate">importlib.machinery.SourceFileLoader.load_module()</code></a> and <a class="reference internal" href="../library/importlib.html#importlib.machinery.SourcelessFileLoader.load_module" title="importlib.machinery.SourcelessFileLoader.load_module"><code class="xref py py-meth docutils literal notranslate">importlib.machinery.SourcelessFileLoader.load_module()</code></a> methods are now deprecated. They were the only remaining implementations of <a class="reference internal" href="../library/importlib.html#importlib.abc.Loader.load_module" title="importlib.abc.Loader.load_module"><code class="xref py py-meth docutils literal notranslate">importlib.abc.Loader.load_module()</code></a> in <a class="reference internal" href="../library/importlib.html#module-importlib" title="importlib: The implementation of the import machinery."><code class="xref py py-mod docutils literal notranslate">importlib</code></a> that had not been deprecated in previous versions of Python in favour of <a class="reference internal" href="../library/importlib.html#importlib.abc.Loader.exec_module" title="importlib.abc.Loader.exec_module"><code class="xref py py-meth docutils literal notranslate">importlib.abc.Loader.exec_module()</code></a>. The <a class="reference internal" href="../library/importlib.html#importlib.machinery.WindowsRegistryFinder" title="importlib.machinery.WindowsRegistryFinder"><code class="xref py py-class docutils literal notranslate">importlib.machinery.WindowsRegistryFinder</code></a> class is now deprecated. As of 3.6.0, it is still added to <a class="reference internal" href="../library/sys.html#sys.meta_path" title="sys.meta_path"><code class="xref py py-data docutils literal notranslate">sys.meta_path</code></a> by default (on Windows), but this may change in future releases. </section> <section id="id4"> <h4>os<a class="headerlink" href="#id4" title="Link to this heading">¶</a></h4> Undocumented support of general <a class="reference internal" href="../glossary.html#term-bytes-like-object">bytes-like objects</a> as paths in <a class="reference internal" href="../library/os.html#module-os" title="os: Miscellaneous operating system interfaces."><code class="xref py py-mod docutils literal notranslate">os</code></a> functions, <a class="reference internal" href="../library/functions.html#compile" title="compile"><code class="xref py py-func docutils literal notranslate">compile()</code></a> and similar functions is now deprecated. (Contributed by Serhiy Storchaka in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=25791">bpo-25791</a> and <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=26754">bpo-26754</a>.) </section> <section id="id5"> <h4>re<a class="headerlink" href="#id5" title="Link to this heading">¶</a></h4> Support for inline flags <code class="docutils literal notranslate">(?letters)</code> in the middle of the regular expression has been deprecated and will be removed in a future Python version. Flags at the start of a regular expression are still allowed. (Contributed by Serhiy Storchaka in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=22493">bpo-22493</a>.) </section> <section id="id6"> <h4>ssl<a class="headerlink" href="#id6" title="Link to this heading">¶</a></h4> OpenSSL 0.9.8, 1.0.0 and 1.0.1 are deprecated and no longer supported. In the future the <a class="reference internal" href="../library/ssl.html#module-ssl" title="ssl: TLS/SSL wrapper for socket objects"><code class="xref py py-mod docutils literal notranslate">ssl</code></a> module will require at least OpenSSL 1.0.2 or 1.1.0. SSL-related arguments like <code class="docutils literal notranslate">certfile</code>, <code class="docutils literal notranslate">keyfile</code> and <code class="docutils literal notranslate">check_hostname</code> in <a class="reference internal" href="../library/ftplib.html#module-ftplib" title="ftplib: FTP protocol client (requires sockets)."><code class="xref py py-mod docutils literal notranslate">ftplib</code></a>, <a class="reference internal" href="../library/http.client.html#module-http.client" title="http.client: HTTP and HTTPS protocol client (requires sockets)."><code class="xref py py-mod docutils literal notranslate">http.client</code></a>, <a class="reference internal" href="../library/imaplib.html#module-imaplib" title="imaplib: IMAP4 protocol client (requires sockets)."><code class="xref py py-mod docutils literal notranslate">imaplib</code></a>, <a class="reference internal" href="../library/poplib.html#module-poplib" title="poplib: POP3 protocol client (requires sockets)."><code class="xref py py-mod docutils literal notranslate">poplib</code></a>, and <a class="reference internal" href="../library/smtplib.html#module-smtplib" title="smtplib: SMTP protocol client (requires sockets)."><code class="xref py py-mod docutils literal notranslate">smtplib</code></a> have been deprecated in favor of <code class="docutils literal notranslate">context</code>. (Contributed by Christian Heimes in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=28022">bpo-28022</a>.) A couple of protocols and functions of the <a class="reference internal" href="../library/ssl.html#module-ssl" title="ssl: TLS/SSL wrapper for socket objects"><code class="xref py py-mod docutils literal notranslate">ssl</code></a> module are now deprecated. Some features will no longer be available in future versions of OpenSSL. Other features are deprecated in favor of a different API. (Contributed by Christian Heimes in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=28022">bpo-28022</a> and <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=26470">bpo-26470</a>.) </section> <section id="id7"> <h4>tkinter<a class="headerlink" href="#id7" title="Link to this heading">¶</a></h4> The <code class="xref py py-mod docutils literal notranslate">tkinter.tix</code> module is now deprecated. <a class="reference internal" href="../library/tkinter.html#module-tkinter" title="tkinter: Interface to Tcl/Tk for graphical user interfaces"><code class="xref py py-mod docutils literal notranslate">tkinter</code></a> users should use <a class="reference internal" href="../library/tkinter.ttk.html#module-tkinter.ttk" title="tkinter.ttk: Tk themed widget set"><code class="xref py py-mod docutils literal notranslate">tkinter.ttk</code></a> instead. </section> <section id="whatsnew36-venv"> <h4>venv<a class="headerlink" href="#whatsnew36-venv" title="Link to this heading">¶</a></h4> The <code class="docutils literal notranslate">pyvenv</code> script has been deprecated in favour of <code class="docutils literal notranslate">python3 -m venv</code>. This prevents confusion as to what Python interpreter <code class="docutils literal notranslate">pyvenv</code> is connected to and thus what Python interpreter will be used by the virtual environment. (Contributed by Brett Cannon in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=25154">bpo-25154</a>.) </section> </section> <section id="xml"> <h3>xml<a class="headerlink" href="#xml" title="Link to this heading">¶</a></h3> <ul class="simple"> <li>As mitigation against DTD and external entity retrieval, the <a class="reference internal" href="../library/xml.dom.minidom.html#module-xml.dom.minidom" title="xml.dom.minidom: Minimal Document Object Model (DOM) implementation."><code class="xref py py-mod docutils literal notranslate">xml.dom.minidom</code></a> and <a class="reference internal" href="../library/xml.sax.html#module-xml.sax" title="xml.sax: Package containing SAX2 base classes and convenience functions."><code class="xref py py-mod docutils literal notranslate">xml.sax</code></a> modules no longer process external entities by default. (Contributed by Christian Heimes in <a class="reference external" href="https://github.com/python/cpython/issues/61441">gh-61441</a>.)</li> </ul> </section> <section id="deprecated-functions-and-types-of-the-c-api"> <h3>Deprecated functions and types of the C API<a class="headerlink" href="#deprecated-functions-and-types-of-the-c-api" title="Link to this heading">¶</a></h3> Undocumented functions <code class="xref c c-func docutils literal notranslate">PyUnicode_AsEncodedObject()</code>, <code class="xref c c-func docutils literal notranslate">PyUnicode_AsDecodedObject()</code>, <code class="xref c c-func docutils literal notranslate">PyUnicode_AsEncodedUnicode()</code> and <code class="xref c c-func docutils literal notranslate">PyUnicode_AsDecodedUnicode()</code> are deprecated now. Use the <a class="reference internal" href="../c-api/codec.html#codec-registry">generic codec based API</a> instead. </section> <section id="deprecated-build-options"> <h3>Deprecated Build Options<a class="headerlink" href="#deprecated-build-options" title="Link to this heading">¶</a></h3> The <code class="docutils literal notranslate">--with-system-ffi</code> configure flag is now on by default on non-macOS UNIX platforms. It may be disabled by using <code class="docutils literal notranslate">--without-system-ffi</code>, but using the flag is deprecated and will not be accepted in Python 3.7. macOS is unaffected by this change. Note that many OS distributors already use the <code class="docutils literal notranslate">--with-system-ffi</code> flag when building their system Python. </section> </section> <section id="removed"> <h2>Removed<a class="headerlink" href="#removed" title="Link to this heading">¶</a></h2> <section id="api-and-feature-removals"> <h3>API and Feature Removals<a class="headerlink" href="#api-and-feature-removals" title="Link to this heading">¶</a></h3> <ul class="simple"> <li>Unknown escapes consisting of <code class="docutils literal notranslate">'\'</code> and an ASCII letter in regular expressions will now cause an error. In replacement templates for <a class="reference internal" href="../library/re.html#re.sub" title="re.sub"><code class="xref py py-func docutils literal notranslate">re.sub()</code></a> they are still allowed, but deprecated. The <a class="reference internal" href="../library/re.html#re.LOCALE" title="re.LOCALE"><code class="xref py py-const docutils literal notranslate">re.LOCALE</code></a> flag can now only be used with binary patterns.</li> <li><code class="docutils literal notranslate">inspect.getmoduleinfo()</code> was removed (was deprecated since CPython 3.3). <a class="reference internal" href="../library/inspect.html#inspect.getmodulename" title="inspect.getmodulename"><code class="xref py py-func docutils literal notranslate">inspect.getmodulename()</code></a> should be used for obtaining the module name for a given path. (Contributed by Yury Selivanov in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=13248">bpo-13248</a>.)</li> <li><code class="docutils literal notranslate">traceback.Ignore</code> class and <code class="docutils literal notranslate">traceback.usage</code>, <code class="docutils literal notranslate">traceback.modname</code>, <code class="docutils literal notranslate">traceback.fullmodname</code>, <code class="docutils literal notranslate">traceback.find_lines_from_code</code>, <code class="docutils literal notranslate">traceback.find_lines</code>, <code class="docutils literal notranslate">traceback.find_strings</code>, <code class="docutils literal notranslate">traceback.find_executable_lines</code> methods were removed from the <a class="reference internal" href="../library/traceback.html#module-traceback" title="traceback: Print or retrieve a stack traceback."><code class="xref py py-mod docutils literal notranslate">traceback</code></a> module. They were undocumented methods deprecated since Python 3.2 and equivalent functionality is available from private methods.</li> <li>The <code class="docutils literal notranslate">tk_menuBar()</code> and <code class="docutils literal notranslate">tk_bindForTraversal()</code> dummy methods in <a class="reference internal" href="../library/tkinter.html#module-tkinter" title="tkinter: Interface to Tcl/Tk for graphical user interfaces"><code class="xref py py-mod docutils literal notranslate">tkinter</code></a> widget classes were removed (corresponding Tk commands were obsolete since Tk 4.0).</li> <li>The <a class="reference internal" href="../library/zipfile.html#zipfile.ZipFile.open" title="zipfile.ZipFile.open"><code class="xref py py-meth docutils literal notranslate">open()</code></a> method of the <a class="reference internal" href="../library/zipfile.html#zipfile.ZipFile" title="zipfile.ZipFile"><code class="xref py py-class docutils literal notranslate">zipfile.ZipFile</code></a> class no longer supports the <code class="docutils literal notranslate">'U'</code> mode (was deprecated since Python 3.4). Use <a class="reference internal" href="../library/io.html#io.TextIOWrapper" title="io.TextIOWrapper"><code class="xref py py-class docutils literal notranslate">io.TextIOWrapper</code></a> for reading compressed text files in <a class="reference internal" href="../glossary.html#term-universal-newlines">universal newlines</a> mode.</li> <li>The undocumented <code class="docutils literal notranslate">IN</code>, <code class="docutils literal notranslate">CDROM</code>, <code class="docutils literal notranslate">DLFCN</code>, <code class="docutils literal notranslate">TYPES</code>, <code class="docutils literal notranslate">CDIO</code>, and <code class="docutils literal notranslate">STROPTS</code> modules have been removed. They had been available in the platform specific <code class="docutils literal notranslate">Lib/plat-*/</code> directories, but were chronically out of date, inconsistently available across platforms, and unmaintained. The script that created these modules is still available in the source distribution at <a class="reference external" href="https://github.com/python/cpython/blob/v3.6.15/Tools/scripts/h2py.py">Tools/scripts/h2py.py</a>.</li> <li>The deprecated <code class="docutils literal notranslate">asynchat.fifo</code> class has been removed.</li> </ul> </section> </section> <section id="porting-to-python-3-6"> <h2>Porting to Python 3.6<a class="headerlink" href="#porting-to-python-3-6" title="Link to this heading">¶</a></h2> This section lists previously described changes and other bugfixes that may require changes to your code. <section id="changes-in-python-command-behavior"> <h3>Changes in ‘python’ Command Behavior<a class="headerlink" href="#changes-in-python-command-behavior" title="Link to this heading">¶</a></h3> <ul class="simple"> <li>The output of a special Python build with defined <code class="docutils literal notranslate">COUNT_ALLOCS</code>, <code class="docutils literal notranslate">SHOW_ALLOC_COUNT</code> or <code class="docutils literal notranslate">SHOW_TRACK_COUNT</code> macros is now off by default. It can be re-enabled using the <code class="docutils literal notranslate">-X showalloccount</code> option. It now outputs to <code class="docutils literal notranslate">stderr</code> instead of <code class="docutils literal notranslate">stdout</code>. (Contributed by Serhiy Storchaka in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=23034">bpo-23034</a>.)</li> </ul> </section> <section id="changes-in-the-python-api"> <h3>Changes in the Python API<a class="headerlink" href="#changes-in-the-python-api" title="Link to this heading">¶</a></h3> <ul> <li><a class="reference internal" href="../library/functions.html#open" title="open"><code class="xref py py-func docutils literal notranslate">open()</code></a> will no longer allow combining the <code class="docutils literal notranslate">'U'</code> mode flag with <code class="docutils literal notranslate">'+'</code>. (Contributed by Jeff Balogh and John O’Connor in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=2091">bpo-2091</a>.)</li> <li><a class="reference internal" href="../library/sqlite3.html#module-sqlite3" title="sqlite3: A DB-API 2.0 implementation using SQLite 3.x."><code class="xref py py-mod docutils literal notranslate">sqlite3</code></a> no longer implicitly commits an open transaction before DDL statements.</li> <li>On Linux, <a class="reference internal" href="../library/os.html#os.urandom" title="os.urandom"><code class="xref py py-func docutils literal notranslate">os.urandom()</code></a> now blocks until the system urandom entropy pool is initialized to increase the security.</li> <li>When <a class="reference internal" href="../library/importlib.html#importlib.abc.Loader.exec_module" title="importlib.abc.Loader.exec_module"><code class="xref py py-meth docutils literal notranslate">importlib.abc.Loader.exec_module()</code></a> is defined, <a class="reference internal" href="../library/importlib.html#importlib.abc.Loader.create_module" title="importlib.abc.Loader.create_module"><code class="xref py py-meth docutils literal notranslate">importlib.abc.Loader.create_module()</code></a> must also be defined.</li> <li><a class="reference internal" href="../c-api/exceptions.html#c.PyErr_SetImportError" title="PyErr_SetImportError"><code class="xref c c-func docutils literal notranslate">PyErr_SetImportError()</code></a> now sets <a class="reference internal" href="../library/exceptions.html#TypeError" title="TypeError"><code class="xref py py-exc docutils literal notranslate">TypeError</code></a> when its msg argument is not set. Previously only <code class="docutils literal notranslate">NULL</code> was returned.</li> <li>The format of the <a class="reference internal" href="../reference/datamodel.html#codeobject.co_lnotab" title="codeobject.co_lnotab"><code class="xref py py-attr docutils literal notranslate">co_lnotab</code></a> attribute of code objects changed to support a negative line number delta. By default, Python does not emit bytecode with a negative line number delta. Functions using <a class="reference internal" href="../reference/datamodel.html#frame.f_lineno" title="frame.f_lineno"><code class="xref py py-attr docutils literal notranslate">frame.f_lineno</code></a>, <code class="docutils literal notranslate">PyFrame_GetLineNumber()</code> or <code class="docutils literal notranslate">PyCode_Addr2Line()</code> are not affected. Functions directly decoding <code class="xref py py-attr docutils literal notranslate">co_lnotab</code> should be updated to use a signed 8-bit integer type for the line number delta, but this is only required to support applications using a negative line number delta. See <code class="docutils literal notranslate">Objects/lnotab_notes.txt</code> for the <code class="xref py py-attr docutils literal notranslate">co_lnotab</code> format and how to decode it, and see the <a class="pep reference external" href="https://peps.python.org/pep-0511/">PEP 511</a> for the rationale.</li> <li>The functions in the <a class="reference internal" href="../library/compileall.html#module-compileall" title="compileall: Tools for byte-compiling all Python source files in a directory tree."><code class="xref py py-mod docutils literal notranslate">compileall</code></a> module now return booleans instead of <code class="docutils literal notranslate">1</code> or <code class="docutils literal notranslate">0</code> to represent success or failure, respectively. Thanks to booleans being a subclass of integers, this should only be an issue if you were doing identity checks for <code class="docutils literal notranslate">1</code> or <code class="docutils literal notranslate">0</code>. See <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=25768">bpo-25768</a>.</li> <li>Reading the <code class="xref py py-attr docutils literal notranslate">port</code> attribute of <a class="reference internal" href="../library/urllib.parse.html#urllib.parse.urlsplit" title="urllib.parse.urlsplit"><code class="xref py py-func docutils literal notranslate">urllib.parse.urlsplit()</code></a> and <a class="reference internal" href="../library/urllib.parse.html#urllib.parse.urlparse" title="urllib.parse.urlparse"><code class="xref py py-func docutils literal notranslate">urlparse()</code></a> results now raises <a class="reference internal" href="../library/exceptions.html#ValueError" title="ValueError"><code class="xref py py-exc docutils literal notranslate">ValueError</code></a> for out-of-range values, rather than returning <a class="reference internal" href="../library/constants.html#None" title="None"><code class="xref py py-const docutils literal notranslate">None</code></a>. See <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=20059">bpo-20059</a>.</li> <li>The <code class="xref py py-mod docutils literal notranslate">imp</code> module now raises a <a class="reference internal" href="../library/exceptions.html#DeprecationWarning" title="DeprecationWarning"><code class="xref py py-exc docutils literal notranslate">DeprecationWarning</code></a> instead of <a class="reference internal" href="../library/exceptions.html#PendingDeprecationWarning" title="PendingDeprecationWarning"><code class="xref py py-exc docutils literal notranslate">PendingDeprecationWarning</code></a>.</li> <li>The following modules have had missing APIs added to their <code class="xref py py-attr docutils literal notranslate">__all__</code> attributes to match the documented APIs: <a class="reference internal" href="../library/calendar.html#module-calendar" title="calendar: Functions for working with calendars, including some emulation of the Unix cal program."><code class="xref py py-mod docutils literal notranslate">calendar</code></a>, <code class="xref py py-mod docutils literal notranslate">cgi</code>, <a class="reference internal" href="../library/csv.html#module-csv" title="csv: Write and read tabular data to and from delimited files."><code class="xref py py-mod docutils literal notranslate">csv</code></a>, <a class="reference internal" href="../library/xml.etree.elementtree.html#module-xml.etree.ElementTree" title="xml.etree.ElementTree: Implementation of the ElementTree API."><code class="xref py py-mod docutils literal notranslate">ElementTree</code></a>, <a class="reference internal" href="../library/enum.html#module-enum" title="enum: Implementation of an enumeration class."><code class="xref py py-mod docutils literal notranslate">enum</code></a>, <a class="reference internal" href="../library/fileinput.html#module-fileinput" title="fileinput: Loop over standard input or a list of files."><code class="xref py py-mod docutils literal notranslate">fileinput</code></a>, <a class="reference internal" href="../library/ftplib.html#module-ftplib" title="ftplib: FTP protocol client (requires sockets)."><code class="xref py py-mod docutils literal notranslate">ftplib</code></a>, <a class="reference internal" href="../library/logging.html#module-logging" title="logging: Flexible event logging system for applications."><code class="xref py py-mod docutils literal notranslate">logging</code></a>, <a class="reference internal" href="../library/mailbox.html#module-mailbox" title="mailbox: Manipulate mailboxes in various formats"><code class="xref py py-mod docutils literal notranslate">mailbox</code></a>, <a class="reference internal" href="../library/mimetypes.html#module-mimetypes" title="mimetypes: Mapping of filename extensions to MIME types."><code class="xref py py-mod docutils literal notranslate">mimetypes</code></a>, <a class="reference internal" href="../library/optparse.html#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate">optparse</code></a>, <a class="reference internal" href="../library/plistlib.html#module-plistlib" title="plistlib: Generate and parse Apple plist files."><code class="xref py py-mod docutils literal notranslate">plistlib</code></a>, <code class="xref py py-mod docutils literal notranslate">smtpd</code>, <a class="reference internal" href="../library/subprocess.html#module-subprocess" title="subprocess: Subprocess management."><code class="xref py py-mod docutils literal notranslate">subprocess</code></a>, <a class="reference internal" href="../library/tarfile.html#module-tarfile" title="tarfile: Read and write tar-format archive files."><code class="xref py py-mod docutils literal notranslate">tarfile</code></a>, <a class="reference internal" href="../library/threading.html#module-threading" title="threading: Thread-based parallelism."><code class="xref py py-mod docutils literal notranslate">threading</code></a> and <a class="reference internal" href="../library/wave.html#module-wave" title="wave: Provide an interface to the WAV sound format."><code class="xref py py-mod docutils literal notranslate">wave</code></a>. This means they will export new symbols when <code class="docutils literal notranslate">import *</code> is used. (Contributed by Joel Taddei and Jacek Kołodziej in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=23883">bpo-23883</a>.)</li> <li>When performing a relative import, if <code class="docutils literal notranslate">__package__</code> does not compare equal to <code class="docutils literal notranslate">__spec__.parent</code> then <a class="reference internal" href="../library/exceptions.html#ImportWarning" title="ImportWarning"><code class="xref py py-exc docutils literal notranslate">ImportWarning</code></a> is raised. (Contributed by Brett Cannon in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=25791">bpo-25791</a>.)</li> <li>When a relative import is performed and no parent package is known, then <a class="reference internal" href="../library/exceptions.html#ImportError" title="ImportError"><code class="xref py py-exc docutils literal notranslate">ImportError</code></a> will be raised. Previously, <a class="reference internal" href="../library/exceptions.html#SystemError" title="SystemError"><code class="xref py py-exc docutils literal notranslate">SystemError</code></a> could be raised. (Contributed by Brett Cannon in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=18018">bpo-18018</a>.)</li> <li>Servers based on the <a class="reference internal" href="../library/socketserver.html#module-socketserver" title="socketserver: A framework for network servers."><code class="xref py py-mod docutils literal notranslate">socketserver</code></a> module, including those defined in <a class="reference internal" href="../library/http.server.html#module-http.server" title="http.server: HTTP server and request handlers."><code class="xref py py-mod docutils literal notranslate">http.server</code></a>, <a class="reference internal" href="../library/xmlrpc.server.html#module-xmlrpc.server" title="xmlrpc.server: Basic XML-RPC server implementations."><code class="xref py py-mod docutils literal notranslate">xmlrpc.server</code></a> and <a class="reference internal" href="../library/wsgiref.html#module-wsgiref.simple_server" title="wsgiref.simple_server: A simple WSGI HTTP server."><code class="xref py py-mod docutils literal notranslate">wsgiref.simple_server</code></a>, now only catch exceptions derived from <a class="reference internal" href="../library/exceptions.html#Exception" title="Exception"><code class="xref py py-exc docutils literal notranslate">Exception</code></a>. Therefore if a request handler raises an exception like <a class="reference internal" href="../library/exceptions.html#SystemExit" title="SystemExit"><code class="xref py py-exc docutils literal notranslate">SystemExit</code></a> or <a class="reference internal" href="../library/exceptions.html#KeyboardInterrupt" title="KeyboardInterrupt"><code class="xref py py-exc docutils literal notranslate">KeyboardInterrupt</code></a>, <a class="reference internal" href="../library/socketserver.html#socketserver.BaseServer.handle_error" title="socketserver.BaseServer.handle_error"><code class="xref py py-meth docutils literal notranslate">handle_error()</code></a> is no longer called, and the exception will stop a single-threaded server. (Contributed by Martin Panter in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=23430">bpo-23430</a>.)</li> <li><code class="xref py py-func docutils literal notranslate">spwd.getspnam()</code> now raises a <a class="reference internal" href="../library/exceptions.html#PermissionError" title="PermissionError"><code class="xref py py-exc docutils literal notranslate">PermissionError</code></a> instead of <a class="reference internal" href="../library/exceptions.html#KeyError" title="KeyError"><code class="xref py py-exc docutils literal notranslate">KeyError</code></a> if the user doesn’t have privileges.</li> <li>The <a class="reference internal" href="../library/socket.html#socket.socket.close" title="socket.socket.close"><code class="xref py py-meth docutils literal notranslate">socket.socket.close()</code></a> method now raises an exception if an error (e.g. <code class="docutils literal notranslate">EBADF</code>) was reported by the underlying system call. (Contributed by Martin Panter in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=26685">bpo-26685</a>.)</li> <li>The decode_data argument for the <code class="xref py py-class docutils literal notranslate">smtpd.SMTPChannel</code> and <code class="xref py py-class docutils literal notranslate">smtpd.SMTPServer</code> constructors is now <code class="docutils literal notranslate">False</code> by default. This means that the argument passed to <code class="xref py py-meth docutils literal notranslate">process_message()</code> is now a bytes object by default, and <code class="xref py py-meth docutils literal notranslate">process_message()</code> will be passed keyword arguments. Code that has already been updated in accordance with the deprecation warning generated by 3.5 will not be affected.</li> <li>All optional arguments of the <a class="reference internal" href="../library/json.html#json.dump" title="json.dump"><code class="xref py py-func docutils literal notranslate">dump()</code></a>, <a class="reference internal" href="../library/json.html#json.dumps" title="json.dumps"><code class="xref py py-func docutils literal notranslate">dumps()</code></a>, <a class="reference internal" href="../library/json.html#json.load" title="json.load"><code class="xref py py-func docutils literal notranslate">load()</code></a> and <a class="reference internal" href="../library/json.html#json.loads" title="json.loads"><code class="xref py py-func docutils literal notranslate">loads()</code></a> functions and <a class="reference internal" href="../library/json.html#json.JSONEncoder" title="json.JSONEncoder"><code class="xref py py-class docutils literal notranslate">JSONEncoder</code></a> and <a class="reference internal" href="../library/json.html#json.JSONDecoder" title="json.JSONDecoder"><code class="xref py py-class docutils literal notranslate">JSONDecoder</code></a> class constructors in the <a class="reference internal" href="../library/json.html#module-json" title="json: Encode and decode the JSON format."><code class="xref py py-mod docutils literal notranslate">json</code></a> module are now <a class="reference internal" href="../glossary.html#keyword-only-parameter">keyword-only</a>. (Contributed by Serhiy Storchaka in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=18726">bpo-18726</a>.)</li> <li>Subclasses of <a class="reference internal" href="../library/functions.html#type" title="type"><code class="xref py py-class docutils literal notranslate">type</code></a> which don’t override <code class="docutils literal notranslate">type.__new__</code> may no longer use the one-argument form to get the type of an object.</li> <li>As part of <a class="pep reference external" href="https://peps.python.org/pep-0487/">PEP 487</a>, the handling of keyword arguments passed to <a class="reference internal" href="../library/functions.html#type" title="type"><code class="xref py py-class docutils literal notranslate">type</code></a> (other than the metaclass hint, <code class="docutils literal notranslate">metaclass</code>) is now consistently delegated to <a class="reference internal" href="../reference/datamodel.html#object.__init_subclass__" title="object.__init_subclass__"><code class="xref py py-meth docutils literal notranslate">object.__init_subclass__()</code></a>. This means that <code class="xref py py-meth docutils literal notranslate">type.__new__()</code> and <code class="xref py py-meth docutils literal notranslate">type.__init__()</code> both now accept arbitrary keyword arguments, but <a class="reference internal" href="../reference/datamodel.html#object.__init_subclass__" title="object.__init_subclass__"><code class="xref py py-meth docutils literal notranslate">object.__init_subclass__()</code></a> (which is called from <code class="xref py py-meth docutils literal notranslate">type.__new__()</code>) will reject them by default. Custom metaclasses accepting additional keyword arguments will need to adjust their calls to <code class="xref py py-meth docutils literal notranslate">type.__new__()</code> (whether direct or via <a class="reference internal" href="../library/functions.html#super" title="super"><code class="xref py py-class docutils literal notranslate">super</code></a>) accordingly.</li> <li>In <code class="docutils literal notranslate">distutils.command.sdist.sdist</code>, the <code class="docutils literal notranslate">default_format</code> attribute has been removed and is no longer honored. Instead, the gzipped tarfile format is the default on all platforms and no platform-specific selection is made. In environments where distributions are built on Windows and zip distributions are required, configure the project with a <code class="docutils literal notranslate">setup.cfg</code> file containing the following: <div class="highlight-ini notranslate"><div class="highlight"><pre>[sdist] formats=zip </pre></div> </div> This behavior has also been backported to earlier Python versions by Setuptools 26.0.0. </li> <li>In the <a class="reference internal" href="../library/urllib.request.html#module-urllib.request" title="urllib.request: Extensible library for opening URLs."><code class="xref py py-mod docutils literal notranslate">urllib.request</code></a> module and the <a class="reference internal" href="../library/http.client.html#http.client.HTTPConnection.request" title="http.client.HTTPConnection.request"><code class="xref py py-meth docutils literal notranslate">http.client.HTTPConnection.request()</code></a> method, if no Content-Length header field has been specified and the request body is a file object, it is now sent with HTTP 1.1 chunked encoding. If a file object has to be sent to a HTTP 1.0 server, the Content-Length value now has to be specified by the caller. (Contributed by Demian Brecht and Rolf Krahl with tweaks from Martin Panter in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=12319">bpo-12319</a>.)</li> <li>The <a class="reference internal" href="../library/csv.html#csv.DictReader" title="csv.DictReader"><code class="xref py py-class docutils literal notranslate">DictReader</code></a> now returns rows of type <a class="reference internal" href="../library/collections.html#collections.OrderedDict" title="collections.OrderedDict"><code class="xref py py-class docutils literal notranslate">OrderedDict</code></a>. (Contributed by Steve Holden in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=27842">bpo-27842</a>.)</li> <li>The <code class="xref py py-const docutils literal notranslate">crypt.METHOD_CRYPT</code> will no longer be added to <code class="docutils literal notranslate">crypt.methods</code> if unsupported by the platform. (Contributed by Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=25287">bpo-25287</a>.)</li> <li>The verbose and rename arguments for <a class="reference internal" href="../library/collections.html#collections.namedtuple" title="collections.namedtuple"><code class="xref py py-func docutils literal notranslate">namedtuple()</code></a> are now keyword-only. (Contributed by Raymond Hettinger in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=25628">bpo-25628</a>.)</li> <li>On Linux, <a class="reference internal" href="../library/ctypes.html#ctypes.util.find_library" title="ctypes.util.find_library"><code class="xref py py-func docutils literal notranslate">ctypes.util.find_library()</code></a> now looks in <code class="docutils literal notranslate">LD_LIBRARY_PATH</code> for shared libraries. (Contributed by Vinay Sajip in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=9998">bpo-9998</a>.)</li> <li>The <a class="reference internal" href="../library/imaplib.html#imaplib.IMAP4" title="imaplib.IMAP4"><code class="xref py py-class docutils literal notranslate">imaplib.IMAP4</code></a> class now handles flags containing the <code class="docutils literal notranslate">']'</code> character in messages sent from the server to improve real-world compatibility. (Contributed by Lita Cho in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=21815">bpo-21815</a>.)</li> <li>The <code class="xref py py-func docutils literal notranslate">mmap.write()</code> function now returns the number of bytes written like other write methods. (Contributed by Jakub Stasiak in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=26335">bpo-26335</a>.)</li> <li>The <a class="reference internal" href="../library/pkgutil.html#pkgutil.iter_modules" title="pkgutil.iter_modules"><code class="xref py py-func docutils literal notranslate">pkgutil.iter_modules()</code></a> and <a class="reference internal" href="../library/pkgutil.html#pkgutil.walk_packages" title="pkgutil.walk_packages"><code class="xref py py-func docutils literal notranslate">pkgutil.walk_packages()</code></a> functions now return <a class="reference internal" href="../library/pkgutil.html#pkgutil.ModuleInfo" title="pkgutil.ModuleInfo"><code class="xref py py-class docutils literal notranslate">ModuleInfo</code></a> named tuples. (Contributed by Ramchandra Apte in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=17211">bpo-17211</a>.)</li> <li><a class="reference internal" href="../library/re.html#re.sub" title="re.sub"><code class="xref py py-func docutils literal notranslate">re.sub()</code></a> now raises an error for invalid numerical group references in replacement templates even if the pattern is not found in the string. The error message for invalid group references now includes the group index and the position of the reference. (Contributed by SilentGhost, Serhiy Storchaka in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=25953">bpo-25953</a>.)</li> <li><a class="reference internal" href="../library/zipfile.html#zipfile.ZipFile" title="zipfile.ZipFile"><code class="xref py py-class docutils literal notranslate">zipfile.ZipFile</code></a> will now raise <a class="reference internal" href="../library/exceptions.html#NotImplementedError" title="NotImplementedError"><code class="xref py py-exc docutils literal notranslate">NotImplementedError</code></a> for unrecognized compression values. Previously a plain <a class="reference internal" href="../library/exceptions.html#RuntimeError" title="RuntimeError"><code class="xref py py-exc docutils literal notranslate">RuntimeError</code></a> was raised. Additionally, calling <a class="reference internal" href="../library/zipfile.html#zipfile.ZipFile" title="zipfile.ZipFile"><code class="xref py py-class docutils literal notranslate">ZipFile</code></a> methods on a closed ZipFile or calling the <a class="reference internal" href="../library/zipfile.html#zipfile.ZipFile.write" title="zipfile.ZipFile.write"><code class="xref py py-meth docutils literal notranslate">write()</code></a> method on a ZipFile created with mode <code class="docutils literal notranslate">'r'</code> will raise a <a class="reference internal" href="../library/exceptions.html#ValueError" title="ValueError"><code class="xref py py-exc docutils literal notranslate">ValueError</code></a>. Previously, a <a class="reference internal" href="../library/exceptions.html#RuntimeError" title="RuntimeError"><code class="xref py py-exc docutils literal notranslate">RuntimeError</code></a> was raised in those scenarios.</li> <li>when custom metaclasses are combined with zero-argument <a class="reference internal" href="../library/functions.html#super" title="super"><code class="xref py py-func docutils literal notranslate">super()</code></a> or direct references from methods to the implicit <code class="docutils literal notranslate">__class__</code> closure variable, the implicit <code class="docutils literal notranslate">__classcell__</code> namespace entry must now be passed up to <code class="docutils literal notranslate">type.__new__</code> for initialisation. Failing to do so will result in a <a class="reference internal" href="../library/exceptions.html#DeprecationWarning" title="DeprecationWarning"><code class="xref py py-exc docutils literal notranslate">DeprecationWarning</code></a> in Python 3.6 and a <a class="reference internal" href="../library/exceptions.html#RuntimeError" title="RuntimeError"><code class="xref py py-exc docutils literal notranslate">RuntimeError</code></a> in Python 3.8.</li> <li>With the introduction of <a class="reference internal" href="../library/exceptions.html#ModuleNotFoundError" title="ModuleNotFoundError"><code class="xref py py-exc docutils literal notranslate">ModuleNotFoundError</code></a>, import system consumers may start expecting import system replacements to raise that more specific exception when appropriate, rather than the less-specific <a class="reference internal" href="../library/exceptions.html#ImportError" title="ImportError"><code class="xref py py-exc docutils literal notranslate">ImportError</code></a>. To provide future compatibility with such consumers, implementers of alternative import systems that completely replace <a class="reference internal" href="../library/functions.html#import__" title="__import__"><code class="xref py py-func docutils literal notranslate">__import__()</code></a> will need to update their implementations to raise the new subclass when a module can’t be found at all. Implementers of compliant plugins to the default import system shouldn’t need to make any changes, as the default import system will raise the new subclass when appropriate.</li> </ul> </section> <section id="changes-in-the-c-api"> <h3>Changes in the C API<a class="headerlink" href="#changes-in-the-c-api" title="Link to this heading">¶</a></h3> <ul class="simple"> <li>The <a class="reference internal" href="../c-api/memory.html#c.PyMem_Malloc" title="PyMem_Malloc"><code class="xref c c-func docutils literal notranslate">PyMem_Malloc()</code></a> allocator family now uses the <a class="reference internal" href="../c-api/memory.html#pymalloc">pymalloc allocator</a> rather than the system <code class="xref c c-func docutils literal notranslate">malloc()</code>. Applications calling <a class="reference internal" href="../c-api/memory.html#c.PyMem_Malloc" title="PyMem_Malloc"><code class="xref c c-func docutils literal notranslate">PyMem_Malloc()</code></a> without holding the GIL can now crash. Set the <a class="reference internal" href="../using/cmdline.html#envvar-PYTHONMALLOC"><code class="xref std std-envvar docutils literal notranslate">PYTHONMALLOC</code></a> environment variable to <code class="docutils literal notranslate">debug</code> to validate the usage of memory allocators in your application. See <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=26249">bpo-26249</a>.</li> <li><a class="reference internal" href="../c-api/sys.html#c.Py_Exit" title="Py_Exit"><code class="xref c c-func docutils literal notranslate">Py_Exit()</code></a> (and the main interpreter) now override the exit status with 120 if flushing buffered data failed. See <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=5319">bpo-5319</a>.</li> </ul> </section> <section id="cpython-bytecode-changes"> <h3>CPython bytecode changes<a class="headerlink" href="#cpython-bytecode-changes" title="Link to this heading">¶</a></h3> There have been several major changes to the <a class="reference internal" href="../glossary.html#term-bytecode">bytecode</a> in Python 3.6. <ul class="simple"> <li>The Python interpreter now uses a 16-bit wordcode instead of bytecode. (Contributed by Demur Rumed with input and reviews from Serhiy Storchaka and Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=26647">bpo-26647</a> and <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=28050">bpo-28050</a>.)</li> <li>The new <code class="xref std std-opcode docutils literal notranslate">FORMAT_VALUE</code> and <a class="reference internal" href="../library/dis.html#opcode-BUILD_STRING"><code class="xref std std-opcode docutils literal notranslate">BUILD_STRING</code></a> opcodes as part of the <a class="reference internal" href="#whatsnew36-pep498">formatted string literal</a> implementation. (Contributed by Eric Smith in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=25483">bpo-25483</a> and Serhiy Storchaka in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=27078">bpo-27078</a>.)</li> <li>The new <a class="reference internal" href="../library/dis.html#opcode-BUILD_CONST_KEY_MAP"><code class="xref std std-opcode docutils literal notranslate">BUILD_CONST_KEY_MAP</code></a> opcode to optimize the creation of dictionaries with constant keys. (Contributed by Serhiy Storchaka in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=27140">bpo-27140</a>.)</li> <li>The function call opcodes have been heavily reworked for better performance and simpler implementation. The <a class="reference internal" href="../library/dis.html#opcode-MAKE_FUNCTION"><code class="xref std std-opcode docutils literal notranslate">MAKE_FUNCTION</code></a>, <code class="xref std std-opcode docutils literal notranslate">CALL_FUNCTION</code>, <code class="xref std std-opcode docutils literal notranslate">CALL_FUNCTION_KW</code> and <code class="xref std std-opcode docutils literal notranslate">BUILD_MAP_UNPACK_WITH_CALL</code> opcodes have been modified, the new <a class="reference internal" href="../library/dis.html#opcode-CALL_FUNCTION_EX"><code class="xref std std-opcode docutils literal notranslate">CALL_FUNCTION_EX</code></a> and <code class="xref std std-opcode docutils literal notranslate">BUILD_TUPLE_UNPACK_WITH_CALL</code> have been added, and <code class="docutils literal notranslate">CALL_FUNCTION_VAR</code>, <code class="docutils literal notranslate">CALL_FUNCTION_VAR_KW</code> and <code class="docutils literal notranslate">MAKE_CLOSURE</code> opcodes have been removed. (Contributed by Demur Rumed in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=27095">bpo-27095</a>, and Serhiy Storchaka in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=27213">bpo-27213</a>, <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=28257">bpo-28257</a>.)</li> <li>The new <a class="reference internal" href="../library/dis.html#opcode-SETUP_ANNOTATIONS"><code class="xref std std-opcode docutils literal notranslate">SETUP_ANNOTATIONS</code></a> and <code class="xref std std-opcode docutils literal notranslate">STORE_ANNOTATION</code> opcodes have been added to support the new <a class="reference internal" href="../glossary.html#term-variable-annotation">variable annotation</a> syntax. (Contributed by Ivan Levkivskyi in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=27985">bpo-27985</a>.)</li> </ul> </section> </section> <section id="notable-changes-in-python-3-6-2"> <h2>Notable changes in Python 3.6.2<a class="headerlink" href="#notable-changes-in-python-3-6-2" title="Link to this heading">¶</a></h2> <section id="new-make-regen-all-build-target"> <h3>New <code class="docutils literal notranslate">make regen-all</code> build target<a class="headerlink" href="#new-make-regen-all-build-target" title="Link to this heading">¶</a></h3> To simplify cross-compilation, and to ensure that CPython can reliably be compiled without requiring an existing version of Python to already be available, the autotools-based build system no longer attempts to implicitly recompile generated files based on file modification times. Instead, a new <code class="docutils literal notranslate">make regen-all</code> command has been added to force regeneration of these files when desired (e.g. after an initial version of Python has already been built based on the pregenerated versions). More selective regeneration targets are also defined - see <a class="extlink-source reference external" href="https://github.com/python/cpython/tree/3.13/Makefile.pre.in">Makefile.pre.in</a> for details. (Contributed by Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=23404">bpo-23404</a>.) <div class="versionadded"> Added in version 3.6.2. </div> </section> <section id="removal-of-make-touch-build-target"> <h3>Removal of <code class="docutils literal notranslate">make touch</code> build target<a class="headerlink" href="#removal-of-make-touch-build-target" title="Link to this heading">¶</a></h3> The <code class="docutils literal notranslate">make touch</code> build target previously used to request implicit regeneration of generated files by updating their modification times has been removed. It has been replaced by the new <code class="docutils literal notranslate">make regen-all</code> target. (Contributed by Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=23404">bpo-23404</a>.) <div class="versionchanged"> Changed in version 3.6.2. </div> </section> </section> <section id="notable-changes-in-python-3-6-4"> <h2>Notable changes in Python 3.6.4<a class="headerlink" href="#notable-changes-in-python-3-6-4" title="Link to this heading">¶</a></h2> The <code class="docutils literal notranslate">PyExc_RecursionErrorInst</code> singleton that was part of the public API has been removed as its members being never cleared may cause a segfault during finalization of the interpreter. (Contributed by Xavier de Gaye in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=22898">bpo-22898</a> and <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=30697">bpo-30697</a>.) </section> <section id="notable-changes-in-python-3-6-5"> <h2>Notable changes in Python 3.6.5<a class="headerlink" href="#notable-changes-in-python-3-6-5" title="Link to this heading">¶</a></h2> The <a class="reference internal" href="../library/locale.html#locale.localeconv" title="locale.localeconv"><code class="xref py py-func docutils literal notranslate">locale.localeconv()</code></a> function now sets temporarily the <code class="docutils literal notranslate">LC_CTYPE</code> locale to the <code class="docutils literal notranslate">LC_NUMERIC</code> locale in some cases. (Contributed by Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=31900">bpo-31900</a>.) </section> <section id="notable-changes-in-python-3-6-7"> <h2>Notable changes in Python 3.6.7<a class="headerlink" href="#notable-changes-in-python-3-6-7" title="Link to this heading">¶</a></h2> <a class="reference internal" href="../library/xml.dom.minidom.html#module-xml.dom.minidom" title="xml.dom.minidom: Minimal Document Object Model (DOM) implementation."><code class="xref py py-mod docutils literal notranslate">xml.dom.minidom</code></a> and <a class="reference internal" href="../library/xml.sax.html#module-xml.sax" title="xml.sax: Package containing SAX2 base classes and convenience functions."><code class="xref py py-mod docutils literal notranslate">xml.sax</code></a> modules no longer process external entities by default. See also <a class="reference external" href="https://github.com/python/cpython/issues/61441">gh-61441</a>. In 3.6.7 the <a class="reference internal" href="../library/tokenize.html#module-tokenize" title="tokenize: Lexical scanner for Python source code."><code class="xref py py-mod docutils literal notranslate">tokenize</code></a> module now implicitly emits a <code class="docutils literal notranslate">NEWLINE</code> token when provided with input that does not have a trailing new line. This behavior now matches what the C tokenizer does internally. (Contributed by Ammar Askar in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=33899">bpo-33899</a>.) </section> <section id="notable-changes-in-python-3-6-10"> <h2>Notable changes in Python 3.6.10<a class="headerlink" href="#notable-changes-in-python-3-6-10" title="Link to this heading">¶</a></h2> Due to significant security concerns, the reuse_address parameter of <a class="reference internal" href="../library/asyncio-eventloop.html#asyncio.loop.create_datagram_endpoint" title="asyncio.loop.create_datagram_endpoint"><code class="xref py py-meth docutils literal notranslate">asyncio.loop.create_datagram_endpoint()</code></a> is no longer supported. This is because of the behavior of the socket option <code class="docutils literal notranslate">SO_REUSEADDR</code> in UDP. For more details, see the documentation for <code class="docutils literal notranslate">loop.create_datagram_endpoint()</code>. (Contributed by Kyle Stanley, Antoine Pitrou, and Yury Selivanov in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=37228">bpo-37228</a>.) </section> <section id="notable-changes-in-python-3-6-13"> <h2>Notable changes in Python 3.6.13<a class="headerlink" href="#notable-changes-in-python-3-6-13" title="Link to this heading">¶</a></h2> Earlier Python versions allowed using both <code class="docutils literal notranslate">;</code> and <code class="docutils literal notranslate">&</code> as query parameter separators in <a class="reference internal" href="../library/urllib.parse.html#urllib.parse.parse_qs" title="urllib.parse.parse_qs"><code class="xref py py-func docutils literal notranslate">urllib.parse.parse_qs()</code></a> and <a class="reference internal" href="../library/urllib.parse.html#urllib.parse.parse_qsl" title="urllib.parse.parse_qsl"><code class="xref py py-func docutils literal notranslate">urllib.parse.parse_qsl()</code></a>. Due to security concerns, and to conform with newer W3C recommendations, this has been changed to allow only a single separator key, with <code class="docutils literal notranslate">&</code> as the default. This change also affects <code class="xref py py-func docutils literal notranslate">cgi.parse()</code> and <code class="xref py py-func docutils literal notranslate">cgi.parse_multipart()</code> as they use the affected functions internally. For more details, please see their respective documentation. (Contributed by Adam Goldschmidt, Senthil Kumaran and Ken Jin in <a class="reference external" href="https://bugs.python.org/issue?@action=redirect&bpo=42967">bpo-42967</a>.) </section> <section id="notable-changes-in-python-3-6-14"> <h2>Notable changes in Python 3.6.14<a class="headerlink" href="#notable-changes-in-python-3-6-14" title="Link to this heading">¶</a></h2> A security fix alters the <a class="reference internal" href="../library/ftplib.html#ftplib.FTP" title="ftplib.FTP"><code class="xref py py-class docutils literal notranslate">ftplib.FTP</code></a> behavior to not trust the IPv4 address sent from the remote server when setting up a passive data channel. We reuse the ftp server IP address instead. For unusual code requiring the old behavior, set a <code class="docutils literal notranslate">trust_server_pasv_ipv4_address</code> attribute on your FTP instance to <code class="docutils literal notranslate">True</code>. (See <a class="reference external" href="https://github.com/python/cpython/issues/87451">gh-87451</a>) The presence of newline or tab characters in parts of a URL allows for some forms of attacks. Following the WHATWG specification that updates RFC 3986, ASCII newline <code class="docutils literal notranslate">\n</code>, <code class="docutils literal notranslate">\r</code> and tab <code class="docutils literal notranslate">\t</code> characters are stripped from the URL by the parser <a class="reference internal" href="../library/urllib.parse.html#module-urllib.parse" title="urllib.parse: Parse URLs into or assemble them from components."><code class="xref py py-func docutils literal notranslate">urllib.parse()</code></a> preventing such attacks. The removal characters are controlled by a new module level variable <code class="docutils literal notranslate">urllib.parse._UNSAFE_URL_BYTES_TO_REMOVE</code>. (See <a class="reference external" href="https://github.com/python/cpython/issues/88048">gh-88048</a>) </section> </section> <div class="clearer"></div> </div> </div> </div> <div class="sphinxsidebar" role="navigation" aria-label="Main"> <div class="sphinxsidebarwrapper"> <div> <h3><a href="../contents.html">Table of Contents</a></h3> <ul> <li><a class="reference internal" href="#">What’s New In Python 3.6</a><ul> <li><a class="reference internal" href="#summary-release-highlights">Summary – Release highlights</a></li> <li><a class="reference internal" href="#new-features">New Features</a><ul> <li><a class="reference internal" href="#pep-498-formatted-string-literals">PEP 498: Formatted string literals</a></li> <li><a class="reference internal" href="#pep-526-syntax-for-variable-annotations">PEP 526: Syntax for variable annotations</a></li> <li><a class="reference internal" href="#pep-515-underscores-in-numeric-literals">PEP 515: Underscores in Numeric Literals</a></li> <li><a class="reference internal" href="#pep-525-asynchronous-generators">PEP 525: Asynchronous Generators</a></li> <li><a class="reference internal" href="#pep-530-asynchronous-comprehensions">PEP 530: Asynchronous Comprehensions</a></li> <li><a class="reference internal" href="#pep-487-simpler-customization-of-class-creation">PEP 487: Simpler customization of class creation</a></li> <li><a class="reference internal" href="#pep-487-descriptor-protocol-enhancements">PEP 487: Descriptor Protocol Enhancements</a></li> <li><a class="reference internal" href="#pep-519-adding-a-file-system-path-protocol">PEP 519: Adding a file system path protocol</a></li> <li><a class="reference internal" href="#pep-495-local-time-disambiguation">PEP 495: Local Time Disambiguation</a></li> <li><a class="reference internal" href="#pep-529-change-windows-filesystem-encoding-to-utf-8">PEP 529: Change Windows filesystem encoding to UTF-8</a></li> <li><a class="reference internal" href="#pep-528-change-windows-console-encoding-to-utf-8">PEP 528: Change Windows console encoding to UTF-8</a></li> <li><a class="reference internal" href="#pep-520-preserving-class-attribute-definition-order">PEP 520: Preserving Class Attribute Definition Order</a></li> <li><a class="reference internal" href="#pep-468-preserving-keyword-argument-order">PEP 468: Preserving Keyword Argument Order</a></li> <li><a class="reference internal" href="#new-dict-implementation">New dict implementation</a></li> <li><a class="reference internal" href="#pep-523-adding-a-frame-evaluation-api-to-cpython">PEP 523: Adding a frame evaluation API to CPython</a></li> <li><a class="reference internal" href="#pythonmalloc-environment-variable">PYTHONMALLOC environment variable</a></li> <li><a class="reference internal" href="#dtrace-and-systemtap-probing-support">DTrace and SystemTap probing support</a></li> </ul> </li> <li><a class="reference internal" href="#other-language-changes">Other Language Changes</a></li> <li><a class="reference internal" href="#new-modules">New Modules</a><ul> <li><a class="reference internal" href="#secrets">secrets</a></li> </ul> </li> <li><a class="reference internal" href="#improved-modules">Improved Modules</a><ul> <li><a class="reference internal" href="#array">array</a></li> <li><a class="reference internal" href="#ast">ast</a></li> <li><a class="reference internal" href="#asyncio">asyncio</a></li> <li><a class="reference internal" href="#binascii">binascii</a></li> <li><a class="reference internal" href="#cmath">cmath</a></li> <li><a class="reference internal" href="#collections">collections</a></li> <li><a class="reference internal" href="#concurrent-futures">concurrent.futures</a></li> <li><a class="reference internal" href="#contextlib">contextlib</a></li> <li><a class="reference internal" href="#datetime">datetime</a></li> <li><a class="reference internal" href="#decimal">decimal</a></li> <li><a class="reference internal" href="#distutils">distutils</a></li> <li><a class="reference internal" href="#email">email</a></li> <li><a class="reference internal" href="#encodings">encodings</a></li> <li><a class="reference internal" href="#enum">enum</a></li> <li><a class="reference internal" href="#faulthandler">faulthandler</a></li> <li><a class="reference internal" href="#fileinput">fileinput</a></li> <li><a class="reference internal" href="#hashlib">hashlib</a></li> <li><a class="reference internal" href="#http-client">http.client</a></li> <li><a class="reference internal" href="#idlelib-and-idle">idlelib and IDLE</a></li> <li><a class="reference internal" href="#importlib">importlib</a></li> <li><a class="reference internal" href="#inspect">inspect</a></li> <li><a class="reference internal" href="#json">json</a></li> <li><a class="reference internal" href="#logging">logging</a></li> <li><a class="reference internal" href="#math">math</a></li> <li><a class="reference internal" href="#multiprocessing">multiprocessing</a></li> <li><a class="reference internal" href="#os">os</a></li> <li><a class="reference internal" href="#pathlib">pathlib</a></li> <li><a class="reference internal" href="#pdb">pdb</a></li> <li><a class="reference internal" href="#pickle">pickle</a></li> <li><a class="reference internal" href="#pickletools">pickletools</a></li> <li><a class="reference internal" href="#pydoc">pydoc</a></li> <li><a class="reference internal" href="#random">random</a></li> <li><a class="reference internal" href="#re">re</a></li> <li><a class="reference internal" href="#readline">readline</a></li> <li><a class="reference internal" href="#rlcompleter">rlcompleter</a></li> <li><a class="reference internal" href="#shlex">shlex</a></li> <li><a class="reference internal" href="#site">site</a></li> <li><a class="reference internal" href="#sqlite3">sqlite3</a></li> <li><a class="reference internal" href="#socket">socket</a></li> <li><a class="reference internal" href="#socketserver">socketserver</a></li> <li><a class="reference internal" href="#ssl">ssl</a></li> <li><a class="reference internal" href="#statistics">statistics</a></li> <li><a class="reference internal" href="#struct">struct</a></li> <li><a class="reference internal" href="#subprocess">subprocess</a></li> <li><a class="reference internal" href="#sys">sys</a></li> <li><a class="reference internal" href="#telnetlib">telnetlib</a></li> <li><a class="reference internal" href="#time">time</a></li> <li><a class="reference internal" href="#timeit">timeit</a></li> <li><a class="reference internal" href="#tkinter">tkinter</a></li> <li><a class="reference internal" href="#traceback">traceback</a></li> <li><a class="reference internal" href="#tracemalloc">tracemalloc</a></li> <li><a class="reference internal" href="#typing">typing</a></li> <li><a class="reference internal" href="#unicodedata">unicodedata</a></li> <li><a class="reference internal" href="#unittest-mock">unittest.mock</a></li> <li><a class="reference internal" href="#urllib-request">urllib.request</a></li> <li><a class="reference internal" href="#urllib-robotparser">urllib.robotparser</a></li> <li><a class="reference internal" href="#venv">venv</a></li> <li><a class="reference internal" href="#warnings">warnings</a></li> <li><a class="reference internal" href="#winreg">winreg</a></li> <li><a class="reference internal" href="#winsound">winsound</a></li> <li><a class="reference internal" href="#xmlrpc-client">xmlrpc.client</a></li> <li><a class="reference internal" href="#zipfile">zipfile</a></li> <li><a class="reference internal" href="#zlib">zlib</a></li> </ul> </li> <li><a class="reference internal" href="#optimizations">Optimizations</a></li> <li><a class="reference internal" href="#build-and-c-api-changes">Build and C API Changes</a></li> <li><a class="reference internal" href="#other-improvements">Other Improvements</a></li> <li><a class="reference internal" href="#deprecated">Deprecated</a><ul> <li><a class="reference internal" href="#new-keywords">New Keywords</a></li> <li><a class="reference internal" href="#deprecated-python-behavior">Deprecated Python behavior</a></li> <li><a class="reference internal" href="#deprecated-python-modules-functions-and-methods">Deprecated Python modules, functions and methods</a><ul> <li><a class="reference internal" href="#asynchat">asynchat</a></li> <li><a class="reference internal" href="#asyncore">asyncore</a></li> <li><a class="reference internal" href="#dbm">dbm</a></li> <li><a class="reference internal" href="#id2">distutils</a></li> <li><a class="reference internal" href="#grp">grp</a></li> <li><a class="reference internal" href="#id3">importlib</a></li> <li><a class="reference internal" href="#id4">os</a></li> <li><a class="reference internal" href="#id5">re</a></li> <li><a class="reference internal" href="#id6">ssl</a></li> <li><a class="reference internal" href="#id7">tkinter</a></li> <li><a class="reference internal" href="#whatsnew36-venv">venv</a></li> </ul> </li> <li><a class="reference internal" href="#xml">xml</a></li> <li><a class="reference internal" href="#deprecated-functions-and-types-of-the-c-api">Deprecated functions and types of the C API</a></li> <li><a class="reference internal" href="#deprecated-build-options">Deprecated Build Options</a></li> </ul> </li> <li><a class="reference internal" href="#removed">Removed</a><ul> <li><a class="reference internal" href="#api-and-feature-removals">API and Feature Removals</a></li> </ul> </li> <li><a class="reference internal" href="#porting-to-python-3-6">Porting to Python 3.6</a><ul> <li><a class="reference internal" href="#changes-in-python-command-behavior">Changes in ‘python’ Command Behavior</a></li> <li><a class="reference internal" href="#changes-in-the-python-api">Changes in the Python API</a></li> <li><a class="reference internal" href="#changes-in-the-c-api">Changes in the C API</a></li> <li><a class="reference internal" href="#cpython-bytecode-changes">CPython bytecode changes</a></li> </ul> </li> <li><a class="reference internal" href="#notable-changes-in-python-3-6-2">Notable changes in Python 3.6.2</a><ul> <li><a class="reference internal" href="#new-make-regen-all-build-target">New <code class="docutils literal notranslate">make regen-all</code> build target</a></li> <li><a class="reference internal" href="#removal-of-make-touch-build-target">Removal of <code class="docutils literal notranslate">make touch</code> build target</a></li> </ul> </li> <li><a class="reference internal" href="#notable-changes-in-python-3-6-4">Notable changes in Python 3.6.4</a></li> <li><a class="reference internal" href="#notable-changes-in-python-3-6-5">Notable changes in Python 3.6.5</a></li> <li><a class="reference internal" href="#notable-changes-in-python-3-6-7">Notable changes in Python 3.6.7</a></li> <li><a class="reference internal" href="#notable-changes-in-python-3-6-10">Notable changes in Python 3.6.10</a></li> <li><a class="reference internal" href="#notable-changes-in-python-3-6-13">Notable changes in Python 3.6.13</a></li> <li><a class="reference internal" href="#notable-changes-in-python-3-6-14">Notable changes in Python 3.6.14</a></li> </ul> </li> </ul> </div> <div> <h4>Previous topic</h4> <a href="3.7.html" title="previous chapter">What’s New In Python 3.7</a> </div> <div> <h4>Next topic</h4> <a href="3.5.html" title="next chapter">What’s New In Python 3.5</a> </div> <div role="note" aria-label="source link"> <h3>This Page</h3> <ul class="this-page-menu"> <li><a href="../bugs.html">Report a Bug</a></li> <li> <a href="https://github.com/python/cpython/blob/main/Doc/whatsnew/3.6.rst" rel="nofollow">Show Source </a> </li> </ul> </div> </div> <div id="sidebarbutton" title="Collapse sidebar"> « </div> </div> <div class="clearer"></div> </div> <div class="related" role="navigation" aria-label="Related"> <h3>Navigation</h3> <ul> <li class="right" style="margin-right: 10px"> <a 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