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internal" href="#"><code class="xref py py-mod docutils literal notranslate">io</code> — Core tools for working with streams</a><ul> <li><a class="reference internal" href="#overview">Overview</a><ul> <li><a class="reference internal" href="#text-i-o">Text I/O</a></li> <li><a class="reference internal" href="#binary-i-o">Binary I/O</a></li> <li><a class="reference internal" href="#raw-i-o">Raw I/O</a></li> </ul> </li> <li><a class="reference internal" href="#text-encoding">Text Encoding</a><ul> <li><a class="reference internal" href="#opt-in-encodingwarning">Opt-in EncodingWarning</a></li> </ul> </li> <li><a class="reference internal" href="#high-level-module-interface">High-level Module Interface</a><ul> <li><a class="reference internal" href="#io.DEFAULT_BUFFER_SIZE"><code class="docutils literal notranslate">DEFAULT_BUFFER_SIZE</code></a></li> <li><a class="reference internal" href="#io.open"><code class="docutils literal notranslate">open()</code></a></li> <li><a class="reference internal" href="#io.open_code"><code class="docutils literal notranslate">open_code()</code></a></li> <li><a class="reference internal" href="#io.text_encoding"><code class="docutils literal notranslate">text_encoding()</code></a></li> <li><a class="reference internal" href="#io.BlockingIOError"><code class="docutils literal notranslate">BlockingIOError</code></a></li> <li><a class="reference internal" href="#io.UnsupportedOperation"><code class="docutils literal notranslate">UnsupportedOperation</code></a></li> </ul> </li> <li><a class="reference internal" href="#class-hierarchy">Class hierarchy</a><ul> <li><a class="reference internal" href="#i-o-base-classes">I/O Base Classes</a><ul> <li><a class="reference internal" href="#io.IOBase"><code class="docutils literal notranslate">IOBase</code></a><ul> <li><a class="reference internal" href="#io.IOBase.close"><code class="docutils literal notranslate">close()</code></a></li> <li><a class="reference internal" href="#io.IOBase.closed"><code class="docutils literal notranslate">closed</code></a></li> <li><a class="reference internal" href="#io.IOBase.fileno"><code class="docutils literal notranslate">fileno()</code></a></li> <li><a class="reference internal" href="#io.IOBase.flush"><code class="docutils literal notranslate">flush()</code></a></li> <li><a class="reference internal" href="#io.IOBase.isatty"><code class="docutils literal notranslate">isatty()</code></a></li> <li><a class="reference internal" href="#io.IOBase.readable"><code class="docutils literal notranslate">readable()</code></a></li> <li><a class="reference internal" href="#io.IOBase.readline"><code class="docutils literal notranslate">readline()</code></a></li> <li><a class="reference internal" href="#io.IOBase.readlines"><code class="docutils literal notranslate">readlines()</code></a></li> <li><a class="reference internal" href="#io.IOBase.seek"><code class="docutils literal notranslate">seek()</code></a></li> <li><a class="reference internal" href="#io.IOBase.seekable"><code class="docutils literal notranslate">seekable()</code></a></li> <li><a class="reference internal" href="#io.IOBase.tell"><code class="docutils literal notranslate">tell()</code></a></li> <li><a class="reference internal" href="#io.IOBase.truncate"><code class="docutils literal notranslate">truncate()</code></a></li> <li><a class="reference internal" href="#io.IOBase.writable"><code class="docutils literal notranslate">writable()</code></a></li> <li><a class="reference internal" href="#io.IOBase.writelines"><code class="docutils literal notranslate">writelines()</code></a></li> <li><a class="reference internal" href="#io.IOBase.__del__"><code class="docutils literal notranslate">__del__()</code></a></li> </ul> </li> <li><a class="reference internal" href="#io.RawIOBase"><code class="docutils literal notranslate">RawIOBase</code></a><ul> <li><a class="reference internal" href="#io.RawIOBase.read"><code class="docutils literal notranslate">read()</code></a></li> <li><a class="reference internal" href="#io.RawIOBase.readall"><code class="docutils literal notranslate">readall()</code></a></li> <li><a class="reference internal" href="#io.RawIOBase.readinto"><code class="docutils literal notranslate">readinto()</code></a></li> <li><a class="reference internal" href="#io.RawIOBase.write"><code class="docutils literal notranslate">write()</code></a></li> </ul> </li> <li><a class="reference internal" href="#io.BufferedIOBase"><code class="docutils literal notranslate">BufferedIOBase</code></a><ul> <li><a class="reference internal" href="#io.BufferedIOBase.raw"><code class="docutils literal notranslate">raw</code></a></li> <li><a class="reference internal" href="#io.BufferedIOBase.detach"><code class="docutils literal notranslate">detach()</code></a></li> <li><a class="reference internal" href="#io.BufferedIOBase.read"><code class="docutils literal notranslate">read()</code></a></li> <li><a class="reference internal" href="#io.BufferedIOBase.read1"><code class="docutils literal notranslate">read1()</code></a></li> <li><a class="reference internal" href="#io.BufferedIOBase.readinto"><code class="docutils literal notranslate">readinto()</code></a></li> <li><a class="reference internal" href="#io.BufferedIOBase.readinto1"><code class="docutils literal notranslate">readinto1()</code></a></li> <li><a class="reference internal" href="#io.BufferedIOBase.write"><code class="docutils literal notranslate">write()</code></a></li> </ul> </li> </ul> </li> <li><a class="reference internal" href="#raw-file-i-o">Raw File I/O</a><ul> <li><a class="reference internal" href="#io.FileIO"><code class="docutils literal notranslate">FileIO</code></a><ul> <li><a class="reference internal" href="#io.FileIO.mode"><code class="docutils literal notranslate">mode</code></a></li> <li><a class="reference internal" href="#io.FileIO.name"><code class="docutils literal notranslate">name</code></a></li> </ul> </li> </ul> </li> <li><a class="reference internal" href="#buffered-streams">Buffered Streams</a><ul> <li><a class="reference internal" href="#io.BytesIO"><code class="docutils literal notranslate">BytesIO</code></a><ul> <li><a class="reference internal" href="#io.BytesIO.getbuffer"><code class="docutils literal notranslate">getbuffer()</code></a></li> <li><a class="reference internal" href="#io.BytesIO.getvalue"><code class="docutils literal notranslate">getvalue()</code></a></li> <li><a class="reference internal" href="#io.BytesIO.read1"><code class="docutils literal notranslate">read1()</code></a></li> <li><a class="reference internal" href="#io.BytesIO.readinto1"><code class="docutils literal notranslate">readinto1()</code></a></li> </ul> </li> <li><a class="reference internal" href="#io.BufferedReader"><code class="docutils literal notranslate">BufferedReader</code></a><ul> <li><a class="reference internal" href="#io.BufferedReader.peek"><code class="docutils literal notranslate">peek()</code></a></li> <li><a class="reference internal" href="#io.BufferedReader.read"><code class="docutils literal notranslate">read()</code></a></li> <li><a class="reference internal" href="#io.BufferedReader.read1"><code class="docutils literal notranslate">read1()</code></a></li> </ul> </li> <li><a class="reference internal" href="#io.BufferedWriter"><code class="docutils literal notranslate">BufferedWriter</code></a><ul> <li><a class="reference internal" href="#io.BufferedWriter.flush"><code class="docutils literal notranslate">flush()</code></a></li> <li><a class="reference internal" href="#io.BufferedWriter.write"><code class="docutils literal notranslate">write()</code></a></li> </ul> </li> <li><a class="reference internal" href="#io.BufferedRandom"><code class="docutils literal notranslate">BufferedRandom</code></a></li> <li><a class="reference internal" href="#io.BufferedRWPair"><code class="docutils literal notranslate">BufferedRWPair</code></a></li> </ul> </li> <li><a class="reference internal" href="#id1">Text I/O</a><ul> <li><a class="reference internal" href="#io.TextIOBase"><code class="docutils literal notranslate">TextIOBase</code></a><ul> <li><a class="reference internal" href="#io.TextIOBase.encoding"><code class="docutils literal notranslate">encoding</code></a></li> <li><a class="reference internal" href="#io.TextIOBase.errors"><code class="docutils literal notranslate">errors</code></a></li> <li><a class="reference internal" href="#io.TextIOBase.newlines"><code class="docutils literal notranslate">newlines</code></a></li> <li><a class="reference internal" href="#io.TextIOBase.buffer"><code class="docutils literal notranslate">buffer</code></a></li> <li><a class="reference internal" href="#io.TextIOBase.detach"><code class="docutils literal notranslate">detach()</code></a></li> <li><a class="reference internal" href="#io.TextIOBase.read"><code class="docutils literal notranslate">read()</code></a></li> <li><a class="reference internal" href="#io.TextIOBase.readline"><code class="docutils literal notranslate">readline()</code></a></li> <li><a class="reference internal" href="#io.TextIOBase.seek"><code class="docutils literal notranslate">seek()</code></a></li> <li><a class="reference internal" href="#io.TextIOBase.tell"><code class="docutils literal notranslate">tell()</code></a></li> <li><a class="reference internal" href="#io.TextIOBase.write"><code class="docutils literal notranslate">write()</code></a></li> </ul> </li> <li><a class="reference internal" href="#io.TextIOWrapper"><code class="docutils literal notranslate">TextIOWrapper</code></a><ul> <li><a class="reference internal" href="#io.TextIOWrapper.line_buffering"><code class="docutils literal notranslate">line_buffering</code></a></li> <li><a class="reference internal" href="#io.TextIOWrapper.write_through"><code class="docutils literal notranslate">write_through</code></a></li> <li><a class="reference internal" href="#io.TextIOWrapper.reconfigure"><code class="docutils literal notranslate">reconfigure()</code></a></li> <li><a class="reference internal" href="#io.TextIOWrapper.seek"><code class="docutils literal notranslate">seek()</code></a></li> <li><a class="reference internal" href="#io.TextIOWrapper.tell"><code class="docutils literal notranslate">tell()</code></a></li> </ul> </li> <li><a class="reference internal" href="#io.StringIO"><code class="docutils literal notranslate">StringIO</code></a><ul> <li><a class="reference internal" href="#io.StringIO.getvalue"><code class="docutils literal notranslate">getvalue()</code></a></li> </ul> </li> <li><a class="reference internal" href="#io.IncrementalNewlineDecoder"><code class="docutils literal notranslate">IncrementalNewlineDecoder</code></a></li> </ul> </li> </ul> </li> <li><a class="reference internal" href="#performance">Performance</a><ul> <li><a class="reference internal" href="#id2">Binary I/O</a></li> <li><a class="reference internal" href="#id3">Text I/O</a></li> <li><a class="reference internal" href="#multi-threading">Multi-threading</a></li> <li><a class="reference internal" href="#reentrancy">Reentrancy</a></li> </ul> </li> </ul> </li> </ul> </div> <div> <h4>Previous topic</h4> <a href="os.html" title="previous chapter"><code class="xref py py-mod docutils literal notranslate">os</code> — Miscellaneous operating system interfaces</a> </div> <div> <h4>Next topic</h4> <a href="time.html" title="next chapter"><code class="xref py py-mod docutils literal notranslate">time</code> — Time access and conversions</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/library/io.rst" rel="nofollow">Show Source </a> </li> </ul> </div> </nav> </div> </div> <div class="related" role="navigation" aria-label="Related"> <h3>Navigation</h3> <ul> <li class="right" style="margin-right: 10px"> <a href="../genindex.html" title="General Index" accesskey="I">index</a></li> <li class="right" > <a href="../py-modindex.html" title="Python Module Index" >modules</a> |</li> <li class="right" > <a href="time.html" title="time — Time access and conversions" accesskey="N">next</a> |</li> <li class="right" > <a href="os.html" title="os — Miscellaneous operating system interfaces" accesskey="P">previous</a> |</li> <li><img src="../_static/py.svg" alt="Python logo" style="vertical-align: middle; margin-top: -1px"/></li> <li><a href="https://www.python.org/">Python</a> »</li> <li class="switchers"> <div class="language_switcher_placeholder"></div> <div class="version_switcher_placeholder"></div> </li> <li> </li> <li id="cpython-language-and-version"> <a href="../index.html">3.13.0 Documentation</a> » </li> <li class="nav-item nav-item-1"><a href="index.html" >The Python Standard Library</a> »</li> <li class="nav-item nav-item-2"><a href="allos.html" accesskey="U">Generic Operating System Services</a> »</li> <li class="nav-item nav-item-this"><a href=""><code class="xref py py-mod docutils literal notranslate">io</code> — Core tools for working with streams</a></li> <li class="right"> <div class="inline-search" role="search"> <form class="inline-search" action="../search.html" method="get"> <input placeholder="Quick search" aria-label="Quick search" type="search" name="q" id="search-box" /> <input type="submit" value="Go" /> </form> </div> | </li> <li class="right"> <label class="theme-selector-label"> Theme <select class="theme-selector" oninput="activateTheme(this.value)"> <option value="auto" selected>Auto</option> <option value="light">Light</option> <option value="dark">Dark</option> </select> </label> |</li> </ul> </div> <div class="document"> <div class="documentwrapper"> <div class="bodywrapper"> <div class="body" role="main"> <section id="module-io"> <h1><code class="xref py py-mod docutils literal notranslate">io</code> — Core tools for working with streams<a class="headerlink" href="#module-io" title="Link to this heading">¶</a></h1> Source code: <a class="extlink-source reference external" href="https://github.com/python/cpython/tree/3.13/Lib/io.py">Lib/io.py</a> <hr class="docutils" /> <section id="overview"> <h2>Overview<a class="headerlink" href="#overview" title="Link to this heading">¶</a></h2> The <a class="reference internal" href="#module-io" title="io: Core tools for working with streams."><code class="xref py py-mod docutils literal notranslate">io</code></a> module provides Python’s main facilities for dealing with various types of I/O. There are three main types of I/O: text I/O, binary I/O and raw I/O. These are generic categories, and various backing stores can be used for each of them. A concrete object belonging to any of these categories is called a <a class="reference internal" href="../glossary.html#term-file-object">file object</a>. Other common terms are stream and file-like object. Independent of its category, each concrete stream object will also have various capabilities: it can be read-only, write-only, or read-write. It can also allow arbitrary random access (seeking forwards or backwards to any location), or only sequential access (for example in the case of a socket or pipe). All streams are careful about the type of data you give to them. For example giving a <a class="reference internal" href="stdtypes.html#str" title="str"><code class="xref py py-class docutils literal notranslate">str</code></a> object to the <code class="xref py py-meth docutils literal notranslate">write()</code> method of a binary stream will raise a <a class="reference internal" href="exceptions.html#TypeError" title="TypeError"><code class="xref py py-exc docutils literal notranslate">TypeError</code></a>. So will giving a <a class="reference internal" href="stdtypes.html#bytes" title="bytes"><code class="xref py py-class docutils literal notranslate">bytes</code></a> object to the <code class="xref py py-meth docutils literal notranslate">write()</code> method of a text stream. <div class="versionchanged"> Changed in version 3.3: Operations that used to raise <a class="reference internal" href="exceptions.html#IOError" title="IOError"><code class="xref py py-exc docutils literal notranslate">IOError</code></a> now raise <a class="reference internal" href="exceptions.html#OSError" title="OSError"><code class="xref py py-exc docutils literal notranslate">OSError</code></a>, since <a class="reference internal" href="exceptions.html#IOError" title="IOError"><code class="xref py py-exc docutils literal notranslate">IOError</code></a> is now an alias of <a class="reference internal" href="exceptions.html#OSError" title="OSError"><code class="xref py py-exc docutils literal notranslate">OSError</code></a>. </div> <section id="text-i-o"> <h3>Text I/O<a class="headerlink" href="#text-i-o" title="Link to this heading">¶</a></h3> Text I/O expects and produces <a class="reference internal" href="stdtypes.html#str" title="str"><code class="xref py py-class docutils literal notranslate">str</code></a> objects. This means that whenever the backing store is natively made of bytes (such as in the case of a file), encoding and decoding of data is made transparently as well as optional translation of platform-specific newline characters. The easiest way to create a text stream is with <a class="reference internal" href="functions.html#open" title="open"><code class="xref py py-meth docutils literal notranslate">open()</code></a>, optionally specifying an encoding: <div class="highlight-python3 notranslate"><div class="highlight"><pre>f = open("myfile.txt", "r", encoding="utf-8") </pre></div> </div> In-memory text streams are also available as <a class="reference internal" href="#io.StringIO" title="io.StringIO"><code class="xref py py-class docutils literal notranslate">StringIO</code></a> objects: <div class="highlight-python3 notranslate"><div class="highlight"><pre>f = io.StringIO("some initial text data") </pre></div> </div> The text stream API is described in detail in the documentation of <a class="reference internal" href="#io.TextIOBase" title="io.TextIOBase"><code class="xref py py-class docutils literal notranslate">TextIOBase</code></a>. </section> <section id="binary-i-o"> <h3>Binary I/O<a class="headerlink" href="#binary-i-o" title="Link to this heading">¶</a></h3> Binary I/O (also called buffered I/O) expects <a class="reference internal" href="../glossary.html#term-bytes-like-object">bytes-like objects</a> and produces <a class="reference internal" href="stdtypes.html#bytes" title="bytes"><code class="xref py py-class docutils literal notranslate">bytes</code></a> objects. No encoding, decoding, or newline translation is performed. This category of streams can be used for all kinds of non-text data, and also when manual control over the handling of text data is desired. The easiest way to create a binary stream is with <a class="reference internal" href="functions.html#open" title="open"><code class="xref py py-meth docutils literal notranslate">open()</code></a> with <code class="docutils literal notranslate">'b'</code> in the mode string: <div class="highlight-python3 notranslate"><div class="highlight"><pre>f = open("myfile.jpg", "rb") </pre></div> </div> In-memory binary streams are also available as <a class="reference internal" href="#io.BytesIO" title="io.BytesIO"><code class="xref py py-class docutils literal notranslate">BytesIO</code></a> objects: <div class="highlight-python3 notranslate"><div class="highlight"><pre>f = io.BytesIO(b"some initial binary data: \x00\x01") </pre></div> </div> The binary stream API is described in detail in the docs of <a class="reference internal" href="#io.BufferedIOBase" title="io.BufferedIOBase"><code class="xref py py-class docutils literal notranslate">BufferedIOBase</code></a>. Other library modules may provide additional ways to create text or binary streams. See <a class="reference internal" href="socket.html#socket.socket.makefile" title="socket.socket.makefile"><code class="xref py py-meth docutils literal notranslate">socket.socket.makefile()</code></a> for example. </section> <section id="raw-i-o"> <h3>Raw I/O<a class="headerlink" href="#raw-i-o" title="Link to this heading">¶</a></h3> Raw I/O (also called unbuffered I/O) is generally used as a low-level building-block for binary and text streams; it is rarely useful to directly manipulate a raw stream from user code. Nevertheless, you can create a raw stream by opening a file in binary mode with buffering disabled: <div class="highlight-python3 notranslate"><div class="highlight"><pre>f = open("myfile.jpg", "rb", buffering=0) </pre></div> </div> The raw stream API is described in detail in the docs of <a class="reference internal" href="#io.RawIOBase" title="io.RawIOBase"><code class="xref py py-class docutils literal notranslate">RawIOBase</code></a>. </section> </section> <section id="text-encoding"> <h2>Text Encoding<a class="headerlink" href="#text-encoding" title="Link to this heading">¶</a></h2> The default encoding of <a class="reference internal" href="#io.TextIOWrapper" title="io.TextIOWrapper"><code class="xref py py-class docutils literal notranslate">TextIOWrapper</code></a> and <a class="reference internal" href="functions.html#open" title="open"><code class="xref py py-func docutils literal notranslate">open()</code></a> is locale-specific (<a class="reference internal" href="locale.html#locale.getencoding" title="locale.getencoding"><code class="xref py py-func docutils literal notranslate">locale.getencoding()</code></a>). However, many developers forget to specify the encoding when opening text files encoded in UTF-8 (e.g. JSON, TOML, Markdown, etc…) since most Unix platforms use UTF-8 locale by default. This causes bugs because the locale encoding is not UTF-8 for most Windows users. For example: <div class="highlight-python3 notranslate"><div class="highlight"><pre># May not work on Windows when non-ASCII characters in the file. with open("README.md") as f: long_description = f.read() </pre></div> </div> Accordingly, it is highly recommended that you specify the encoding explicitly when opening text files. If you want to use UTF-8, pass <code class="docutils literal notranslate">encoding="utf-8"</code>. To use the current locale encoding, <code class="docutils literal notranslate">encoding="locale"</code> is supported since Python 3.10. <div class="admonition seealso"> See also <dl class="simple"> <dt><a class="reference internal" href="os.html#utf8-mode">Python UTF-8 Mode</a></dt><dd>Python UTF-8 Mode can be used to change the default encoding to UTF-8 from locale-specific encoding. </dd> <dt><a class="pep reference external" href="https://peps.python.org/pep-0686/">PEP 686</a></dt><dd>Python 3.15 will make <a class="reference internal" href="os.html#utf8-mode">Python UTF-8 Mode</a> default. </dd> </dl> </div> <section id="opt-in-encodingwarning"> <h3>Opt-in EncodingWarning<a class="headerlink" href="#opt-in-encodingwarning" title="Link to this heading">¶</a></h3> <div class="versionadded"> Added in version 3.10: See <a class="pep reference external" href="https://peps.python.org/pep-0597/">PEP 597</a> for more details. </div> To find where the default locale encoding is used, you can enable the <a class="reference internal" href="../using/cmdline.html#cmdoption-X"><code class="xref std std-option docutils literal notranslate">-X warn_default_encoding</code></a> command line option or set the <a class="reference internal" href="../using/cmdline.html#envvar-PYTHONWARNDEFAULTENCODING"><code class="xref std std-envvar docutils literal notranslate">PYTHONWARNDEFAULTENCODING</code></a> environment variable, which will emit an <a class="reference internal" href="exceptions.html#EncodingWarning" title="EncodingWarning"><code class="xref py py-exc docutils literal notranslate">EncodingWarning</code></a> when the default encoding is used. If you are providing an API that uses <a class="reference internal" href="functions.html#open" title="open"><code class="xref py py-func docutils literal notranslate">open()</code></a> or <a class="reference internal" href="#io.TextIOWrapper" title="io.TextIOWrapper"><code class="xref py py-class docutils literal notranslate">TextIOWrapper</code></a> and passes <code class="docutils literal notranslate">encoding=None</code> as a parameter, you can use <a class="reference internal" href="#io.text_encoding" title="io.text_encoding"><code class="xref py py-func docutils literal notranslate">text_encoding()</code></a> so that callers of the API will emit an <a class="reference internal" href="exceptions.html#EncodingWarning" title="EncodingWarning"><code class="xref py py-exc docutils literal notranslate">EncodingWarning</code></a> if they don’t pass an <code class="docutils literal notranslate">encoding</code>. However, please consider using UTF-8 by default (i.e. <code class="docutils literal notranslate">encoding="utf-8"</code>) for new APIs. </section> </section> <section id="high-level-module-interface"> <h2>High-level Module Interface<a class="headerlink" href="#high-level-module-interface" title="Link to this heading">¶</a></h2> <dl class="py data"> <dt class="sig sig-object py" id="io.DEFAULT_BUFFER_SIZE"> io.DEFAULT_BUFFER_SIZE<a class="headerlink" href="#io.DEFAULT_BUFFER_SIZE" title="Link to this definition">¶</a></dt> <dd>An int containing the default buffer size used by the module’s buffered I/O classes. <a class="reference internal" href="functions.html#open" title="open"><code class="xref py py-func docutils literal notranslate">open()</code></a> uses the file’s blksize (as obtained by <a class="reference internal" href="os.html#os.stat" title="os.stat"><code class="xref py py-func docutils literal notranslate">os.stat()</code></a>) if possible. </dd></dl> <dl class="py function"> <dt class="sig sig-object py" id="io.open"> io.open(file, mode='r', buffering=-1, encoding=None, errors=None, newline=None, closefd=True, opener=None)<a class="headerlink" href="#io.open" title="Link to this definition">¶</a></dt> <dd>This is an alias for the builtin <a class="reference internal" href="functions.html#open" title="open"><code class="xref py py-func docutils literal notranslate">open()</code></a> function. This function raises an <a class="reference internal" href="sys.html#auditing">auditing event</a> <code class="docutils literal notranslate">open</code> with arguments path, mode and flags. The mode and flags arguments may have been modified or inferred from the original call. </dd></dl> <dl class="py function"> <dt class="sig sig-object py" id="io.open_code"> io.open_code(path)<a class="headerlink" href="#io.open_code" title="Link to this definition">¶</a></dt> <dd>Opens the provided file with mode <code class="docutils literal notranslate">'rb'</code>. This function should be used when the intent is to treat the contents as executable code. path should be a <a class="reference internal" href="stdtypes.html#str" title="str"><code class="xref py py-class docutils literal notranslate">str</code></a> and an absolute path. The behavior of this function may be overridden by an earlier call to the <a class="reference internal" href="../c-api/file.html#c.PyFile_SetOpenCodeHook" title="PyFile_SetOpenCodeHook"><code class="xref c c-func docutils literal notranslate">PyFile_SetOpenCodeHook()</code></a>. However, assuming that path is a <a class="reference internal" href="stdtypes.html#str" title="str"><code class="xref py py-class docutils literal notranslate">str</code></a> and an absolute path, <code class="docutils literal notranslate">open_code(path)</code> should always behave the same as <code class="docutils literal notranslate">open(path, 'rb')</code>. Overriding the behavior is intended for additional validation or preprocessing of the file. <div class="versionadded"> Added in version 3.8. </div> </dd></dl> <dl class="py function"> <dt class="sig sig-object py" id="io.text_encoding"> io.text_encoding(encoding, stacklevel=2, /)<a class="headerlink" href="#io.text_encoding" title="Link to this definition">¶</a></dt> <dd>This is a helper function for callables that use <a class="reference internal" href="functions.html#open" title="open"><code class="xref py py-func docutils literal notranslate">open()</code></a> or <a class="reference internal" href="#io.TextIOWrapper" title="io.TextIOWrapper"><code class="xref py py-class docutils literal notranslate">TextIOWrapper</code></a> and have an <code class="docutils literal notranslate">encoding=None</code> parameter. This function returns encoding if it is not <code class="docutils literal notranslate">None</code>. Otherwise, it returns <code class="docutils literal notranslate">"locale"</code> or <code class="docutils literal notranslate">"utf-8"</code> depending on <a class="reference internal" href="os.html#utf8-mode">UTF-8 Mode</a>. This function emits an <a class="reference internal" href="exceptions.html#EncodingWarning" title="EncodingWarning"><code class="xref py py-class docutils literal notranslate">EncodingWarning</code></a> if <a class="reference internal" href="sys.html#sys.flags" title="sys.flags"><code class="xref py py-data docutils literal notranslate">sys.flags.warn_default_encoding</code></a> is true and encoding is <code class="docutils literal notranslate">None</code>. stacklevel specifies where the warning is emitted. For example: <div class="highlight-python3 notranslate"><div class="highlight"><pre>def read_text(path, encoding=None): encoding = io.text_encoding(encoding) # stacklevel=2 with open(path, encoding) as f: return f.read() </pre></div> </div> In this example, an <a class="reference internal" href="exceptions.html#EncodingWarning" title="EncodingWarning"><code class="xref py py-class docutils literal notranslate">EncodingWarning</code></a> is emitted for the caller of <code class="docutils literal notranslate">read_text()</code>. See <a class="reference internal" href="#io-text-encoding">Text Encoding</a> for more information. <div class="versionadded"> Added in version 3.10. </div> <div class="versionchanged"> Changed in version 3.11: <a class="reference internal" href="#io.text_encoding" title="io.text_encoding"><code class="xref py py-func docutils literal notranslate">text_encoding()</code></a> returns “utf-8” when UTF-8 mode is enabled and encoding is <code class="docutils literal notranslate">None</code>. </div> </dd></dl> <dl class="py exception"> <dt class="sig sig-object py" id="io.BlockingIOError"> exception io.BlockingIOError<a class="headerlink" href="#io.BlockingIOError" title="Link to this definition">¶</a></dt> <dd>This is a compatibility alias for the builtin <a class="reference internal" href="exceptions.html#BlockingIOError" title="BlockingIOError"><code class="xref py py-exc docutils literal notranslate">BlockingIOError</code></a> exception. </dd></dl> <dl class="py exception"> <dt class="sig sig-object py" id="io.UnsupportedOperation"> exception io.UnsupportedOperation<a class="headerlink" href="#io.UnsupportedOperation" title="Link to this definition">¶</a></dt> <dd>An exception inheriting <a class="reference internal" href="exceptions.html#OSError" title="OSError"><code class="xref py py-exc docutils literal notranslate">OSError</code></a> and <a class="reference internal" href="exceptions.html#ValueError" title="ValueError"><code class="xref py py-exc docutils literal notranslate">ValueError</code></a> that is raised when an unsupported operation is called on a stream. </dd></dl> <div class="admonition seealso"> See also <dl class="simple"> <dt><a class="reference internal" href="sys.html#module-sys" title="sys: Access system-specific parameters and functions."><code class="xref py py-mod docutils literal notranslate">sys</code></a></dt><dd>contains the standard IO streams: <a class="reference internal" href="sys.html#sys.stdin" title="sys.stdin"><code class="xref py py-data docutils literal notranslate">sys.stdin</code></a>, <a class="reference internal" href="sys.html#sys.stdout" title="sys.stdout"><code class="xref py py-data docutils literal notranslate">sys.stdout</code></a>, and <a class="reference internal" href="sys.html#sys.stderr" title="sys.stderr"><code class="xref py py-data docutils literal notranslate">sys.stderr</code></a>. </dd> </dl> </div> </section> <section id="class-hierarchy"> <h2>Class hierarchy<a class="headerlink" href="#class-hierarchy" title="Link to this heading">¶</a></h2> The implementation of I/O streams is organized as a hierarchy of classes. First <a class="reference internal" href="../glossary.html#term-abstract-base-class">abstract base classes</a> (ABCs), which are used to specify the various categories of streams, then concrete classes providing the standard stream implementations. <div class="admonition note"> Note The abstract base classes also provide default implementations of some methods in order to help implementation of concrete stream classes. For example, <a class="reference internal" href="#io.BufferedIOBase" title="io.BufferedIOBase"><code class="xref py py-class docutils literal notranslate">BufferedIOBase</code></a> provides unoptimized implementations of <code class="xref py py-meth docutils literal notranslate">readinto()</code> and <code class="xref py py-meth docutils literal notranslate">readline()</code>. </div> At the top of the I/O hierarchy is the abstract base class <a class="reference internal" href="#io.IOBase" title="io.IOBase"><code class="xref py py-class docutils literal notranslate">IOBase</code></a>. It defines the basic interface to a stream. Note, however, that there is no separation between reading and writing to streams; implementations are allowed to raise <a class="reference internal" href="#io.UnsupportedOperation" title="io.UnsupportedOperation"><code class="xref py py-exc docutils literal notranslate">UnsupportedOperation</code></a> if they do not support a given operation. The <a class="reference internal" href="#io.RawIOBase" title="io.RawIOBase"><code class="xref py py-class docutils literal notranslate">RawIOBase</code></a> ABC extends <a class="reference internal" href="#io.IOBase" title="io.IOBase"><code class="xref py py-class docutils literal notranslate">IOBase</code></a>. It deals with the reading and writing of bytes to a stream. <a class="reference internal" href="#io.FileIO" title="io.FileIO"><code class="xref py py-class docutils literal notranslate">FileIO</code></a> subclasses <a class="reference internal" href="#io.RawIOBase" title="io.RawIOBase"><code class="xref py py-class docutils literal notranslate">RawIOBase</code></a> to provide an interface to files in the machine’s file system. The <a class="reference internal" href="#io.BufferedIOBase" title="io.BufferedIOBase"><code class="xref py py-class docutils literal notranslate">BufferedIOBase</code></a> ABC extends <a class="reference internal" href="#io.IOBase" title="io.IOBase"><code class="xref py py-class docutils literal notranslate">IOBase</code></a>. It deals with buffering on a raw binary stream (<a class="reference internal" href="#io.RawIOBase" title="io.RawIOBase"><code class="xref py py-class docutils literal notranslate">RawIOBase</code></a>). Its subclasses, <a class="reference internal" href="#io.BufferedWriter" title="io.BufferedWriter"><code class="xref py py-class docutils literal notranslate">BufferedWriter</code></a>, <a class="reference internal" href="#io.BufferedReader" title="io.BufferedReader"><code class="xref py py-class docutils literal notranslate">BufferedReader</code></a>, and <a class="reference internal" href="#io.BufferedRWPair" title="io.BufferedRWPair"><code class="xref py py-class docutils literal notranslate">BufferedRWPair</code></a> buffer raw binary streams that are writable, readable, and both readable and writable, respectively. <a class="reference internal" href="#io.BufferedRandom" title="io.BufferedRandom"><code class="xref py py-class docutils literal notranslate">BufferedRandom</code></a> provides a buffered interface to seekable streams. Another <a class="reference internal" href="#io.BufferedIOBase" title="io.BufferedIOBase"><code class="xref py py-class docutils literal notranslate">BufferedIOBase</code></a> subclass, <a class="reference internal" href="#io.BytesIO" title="io.BytesIO"><code class="xref py py-class docutils literal notranslate">BytesIO</code></a>, is a stream of in-memory bytes. The <a class="reference internal" href="#io.TextIOBase" title="io.TextIOBase"><code class="xref py py-class docutils literal notranslate">TextIOBase</code></a> ABC extends <a class="reference internal" href="#io.IOBase" title="io.IOBase"><code class="xref py py-class docutils literal notranslate">IOBase</code></a>. It deals with streams whose bytes represent text, and handles encoding and decoding to and from strings. <a class="reference internal" href="#io.TextIOWrapper" title="io.TextIOWrapper"><code class="xref py py-class docutils literal notranslate">TextIOWrapper</code></a>, which extends <a class="reference internal" href="#io.TextIOBase" title="io.TextIOBase"><code class="xref py py-class docutils literal notranslate">TextIOBase</code></a>, is a buffered text interface to a buffered raw stream (<a class="reference internal" href="#io.BufferedIOBase" title="io.BufferedIOBase"><code class="xref py py-class docutils literal notranslate">BufferedIOBase</code></a>). Finally, <a class="reference internal" href="#io.StringIO" title="io.StringIO"><code class="xref py py-class docutils literal notranslate">StringIO</code></a> is an in-memory stream for text. Argument names are not part of the specification, and only the arguments of <a class="reference internal" href="functions.html#open" title="open"><code class="xref py py-func docutils literal notranslate">open()</code></a> are intended to be used as keyword arguments. The following table summarizes the ABCs provided by the <a class="reference internal" href="#module-io" title="io: Core tools for working with streams."><code class="xref py py-mod docutils literal notranslate">io</code></a> module: <table class="docutils align-default"> <thead> <tr class="row-odd"><th class="head">ABC</th> <th class="head">Inherits</th> <th class="head">Stub Methods</th> <th class="head">Mixin Methods and Properties</th> </tr> </thead> <tbody> <tr class="row-even"><td><a class="reference internal" href="#io.IOBase" title="io.IOBase"><code class="xref py py-class docutils literal notranslate">IOBase</code></a></td> <td></td> <td><code class="docutils literal notranslate">fileno</code>, <code class="docutils literal notranslate">seek</code>, and <code class="docutils literal notranslate">truncate</code></td> <td><code class="docutils literal notranslate">close</code>, <code class="docutils literal notranslate">closed</code>, <code class="docutils literal notranslate">__enter__</code>, <code class="docutils literal notranslate">__exit__</code>, <code class="docutils literal notranslate">flush</code>, <code class="docutils literal notranslate">isatty</code>, <code class="docutils literal notranslate">__iter__</code>, <code class="docutils literal notranslate">__next__</code>, <code class="docutils literal notranslate">readable</code>, <code class="docutils literal notranslate">readline</code>, <code class="docutils literal notranslate">readlines</code>, <code class="docutils literal notranslate">seekable</code>, <code class="docutils literal notranslate">tell</code>, <code class="docutils literal notranslate">writable</code>, and <code class="docutils literal notranslate">writelines</code></td> </tr> <tr class="row-odd"><td><a class="reference internal" href="#io.RawIOBase" title="io.RawIOBase"><code class="xref py py-class docutils literal notranslate">RawIOBase</code></a></td> <td><a class="reference internal" href="#io.IOBase" title="io.IOBase"><code class="xref py py-class docutils literal notranslate">IOBase</code></a></td> <td><code class="docutils literal notranslate">readinto</code> and <code class="docutils literal notranslate">write</code></td> <td>Inherited <a class="reference internal" href="#io.IOBase" title="io.IOBase"><code class="xref py py-class docutils literal notranslate">IOBase</code></a> methods, <code class="docutils literal notranslate">read</code>, and <code class="docutils literal notranslate">readall</code></td> </tr> <tr class="row-even"><td><a class="reference internal" href="#io.BufferedIOBase" title="io.BufferedIOBase"><code class="xref py py-class docutils literal notranslate">BufferedIOBase</code></a></td> <td><a class="reference internal" href="#io.IOBase" title="io.IOBase"><code class="xref py py-class docutils literal notranslate">IOBase</code></a></td> <td><code class="docutils literal notranslate">detach</code>, <code class="docutils literal notranslate">read</code>, <code class="docutils literal notranslate">read1</code>, and <code class="docutils literal notranslate">write</code></td> <td>Inherited <a class="reference internal" href="#io.IOBase" title="io.IOBase"><code class="xref py py-class docutils literal notranslate">IOBase</code></a> methods, <code class="docutils literal notranslate">readinto</code>, and <code class="docutils literal notranslate">readinto1</code></td> </tr> <tr class="row-odd"><td><a class="reference internal" href="#io.TextIOBase" title="io.TextIOBase"><code class="xref py py-class docutils literal notranslate">TextIOBase</code></a></td> <td><a class="reference internal" href="#io.IOBase" title="io.IOBase"><code class="xref py py-class docutils literal notranslate">IOBase</code></a></td> <td><code class="docutils literal notranslate">detach</code>, <code class="docutils literal notranslate">read</code>, <code class="docutils literal notranslate">readline</code>, and <code class="docutils literal notranslate">write</code></td> <td>Inherited <a class="reference internal" href="#io.IOBase" title="io.IOBase"><code class="xref py py-class docutils literal notranslate">IOBase</code></a> methods, <code class="docutils literal notranslate">encoding</code>, <code class="docutils literal notranslate">errors</code>, and <code class="docutils literal notranslate">newlines</code></td> </tr> </tbody> </table> <section id="i-o-base-classes"> <h3>I/O Base Classes<a class="headerlink" href="#i-o-base-classes" title="Link to this heading">¶</a></h3> <dl class="py class"> <dt class="sig sig-object py" id="io.IOBase"> class io.IOBase<a class="headerlink" href="#io.IOBase" title="Link to this definition">¶</a></dt> <dd>The abstract base class for all I/O classes. This class provides empty abstract implementations for many methods that derived classes can override selectively; the default implementations represent a file that cannot be read, written or seeked. Even though <a class="reference internal" href="#io.IOBase" title="io.IOBase"><code class="xref py py-class docutils literal notranslate">IOBase</code></a> does not declare <code class="xref py py-meth docutils literal notranslate">read()</code> or <code class="xref py py-meth docutils literal notranslate">write()</code> because their signatures will vary, implementations and clients should consider those methods part of the interface. Also, implementations may raise a <a class="reference internal" href="exceptions.html#ValueError" title="ValueError"><code class="xref py py-exc docutils literal notranslate">ValueError</code></a> (or <a class="reference internal" href="#io.UnsupportedOperation" title="io.UnsupportedOperation"><code class="xref py py-exc docutils literal notranslate">UnsupportedOperation</code></a>) when operations they do not support are called. The basic type used for binary data read from or written to a file is <a class="reference internal" href="stdtypes.html#bytes" title="bytes"><code class="xref py py-class docutils literal notranslate">bytes</code></a>. Other <a class="reference internal" href="../glossary.html#term-bytes-like-object">bytes-like objects</a> are accepted as method arguments too. Text I/O classes work with <a class="reference internal" href="stdtypes.html#str" title="str"><code class="xref py py-class docutils literal notranslate">str</code></a> data. Note that calling any method (even inquiries) on a closed stream is undefined. Implementations may raise <a class="reference internal" href="exceptions.html#ValueError" title="ValueError"><code class="xref py py-exc docutils literal notranslate">ValueError</code></a> in this case. <a class="reference internal" href="#io.IOBase" title="io.IOBase"><code class="xref py py-class docutils literal notranslate">IOBase</code></a> (and its subclasses) supports the iterator protocol, meaning that an <a class="reference internal" href="#io.IOBase" title="io.IOBase"><code class="xref py py-class docutils literal notranslate">IOBase</code></a> object can be iterated over yielding the lines in a stream. Lines are defined slightly differently depending on whether the stream is a binary stream (yielding bytes), or a text stream (yielding character strings). See <a class="reference internal" href="#io.IOBase.readline" title="io.IOBase.readline"><code class="xref py py-meth docutils literal notranslate">readline()</code></a> below. <a class="reference internal" href="#io.IOBase" title="io.IOBase"><code class="xref py py-class docutils literal notranslate">IOBase</code></a> is also a context manager and therefore supports the <a class="reference internal" href="../reference/compound_stmts.html#with"><code class="xref std std-keyword docutils literal notranslate">with</code></a> statement. In this example, file is closed after the <code class="xref std std-keyword docutils literal notranslate">with</code> statement’s suite is finished—even if an exception occurs: <div class="highlight-python3 notranslate"><div class="highlight"><pre>with open('spam.txt', 'w') as file: file.write('Spam and eggs!') </pre></div> </div> <a class="reference internal" href="#io.IOBase" title="io.IOBase"><code class="xref py py-class docutils literal notranslate">IOBase</code></a> provides these data attributes and methods: <dl class="py method"> <dt class="sig sig-object py" id="io.IOBase.close"> close()<a class="headerlink" href="#io.IOBase.close" title="Link to this definition">¶</a></dt> <dd>Flush and close this stream. This method has no effect if the file is already closed. Once the file is closed, any operation on the file (e.g. reading or writing) will raise a <a class="reference internal" href="exceptions.html#ValueError" title="ValueError"><code class="xref py py-exc docutils literal notranslate">ValueError</code></a>. As a convenience, it is allowed to call this method more than once; only the first call, however, will have an effect. </dd></dl> <dl class="py attribute"> <dt class="sig sig-object py" id="io.IOBase.closed"> closed<a class="headerlink" href="#io.IOBase.closed" title="Link to this definition">¶</a></dt> <dd><code class="docutils literal notranslate">True</code> if the stream is closed. </dd></dl> <dl class="py method"> <dt class="sig sig-object py" id="io.IOBase.fileno"> fileno()<a class="headerlink" href="#io.IOBase.fileno" title="Link to this definition">¶</a></dt> <dd>Return the underlying file descriptor (an integer) of the stream if it exists. An <a class="reference internal" href="exceptions.html#OSError" title="OSError"><code class="xref py py-exc docutils literal notranslate">OSError</code></a> is raised if the IO object does not use a file descriptor. </dd></dl> <dl class="py method"> <dt class="sig sig-object py" id="io.IOBase.flush"> flush()<a class="headerlink" href="#io.IOBase.flush" title="Link to this definition">¶</a></dt> <dd>Flush the write buffers of the stream if applicable. This does nothing for read-only and non-blocking streams. </dd></dl> <dl class="py method"> <dt class="sig sig-object py" id="io.IOBase.isatty"> isatty()<a class="headerlink" href="#io.IOBase.isatty" title="Link to this definition">¶</a></dt> <dd>Return <code class="docutils literal notranslate">True</code> if the stream is interactive (i.e., connected to a terminal/tty device). </dd></dl> <dl class="py method"> <dt class="sig sig-object py" id="io.IOBase.readable"> readable()<a class="headerlink" href="#io.IOBase.readable" title="Link to this definition">¶</a></dt> <dd>Return <code class="docutils literal notranslate">True</code> if the stream can be read from. If <code class="docutils literal notranslate">False</code>, <code class="xref py py-meth docutils literal notranslate">read()</code> will raise <a class="reference internal" href="exceptions.html#OSError" title="OSError"><code class="xref py py-exc docutils literal notranslate">OSError</code></a>. </dd></dl> <dl class="py method"> <dt class="sig sig-object py" id="io.IOBase.readline"> readline(size=-1, /)<a class="headerlink" href="#io.IOBase.readline" title="Link to this definition">¶</a></dt> <dd>Read and return one line from the stream. If size is specified, at most size bytes will be read. The line terminator is always <code class="docutils literal notranslate">b'\n'</code> for binary files; for text files, the newline argument to <a class="reference internal" href="functions.html#open" title="open"><code class="xref py py-func docutils literal notranslate">open()</code></a> can be used to select the line terminator(s) recognized. </dd></dl> <dl class="py method"> <dt class="sig sig-object py" id="io.IOBase.readlines"> readlines(hint=-1, /)<a class="headerlink" href="#io.IOBase.readlines" title="Link to this definition">¶</a></dt> <dd>Read and return a list of lines from the stream. hint can be specified to control the number of lines read: no more lines will be read if the total size (in bytes/characters) of all lines so far exceeds hint. hint values of <code class="docutils literal notranslate">0</code> or less, as well as <code class="docutils literal notranslate">None</code>, are treated as no hint. Note that it’s already possible to iterate on file objects using <code class="docutils literal notranslate">for line in file: ...</code> without calling <code class="xref py py-meth docutils literal notranslate">file.readlines()</code>. </dd></dl> <dl class="py method"> <dt class="sig sig-object py" id="io.IOBase.seek"> seek(offset, whence=os.SEEK_SET, /)<a class="headerlink" href="#io.IOBase.seek" title="Link to this definition">¶</a></dt> <dd>Change the stream position to the given byte offset, interpreted relative to the position indicated by whence, and return the new absolute position. Values for whence are: <ul class="simple"> <li><a class="reference internal" href="os.html#os.SEEK_SET" title="os.SEEK_SET"><code class="xref py py-data docutils literal notranslate">os.SEEK_SET</code></a> or <code class="docutils literal notranslate">0</code> – start of the stream (the default); offset should be zero or positive</li> <li><a class="reference internal" href="os.html#os.SEEK_CUR" title="os.SEEK_CUR"><code class="xref py py-data docutils literal notranslate">os.SEEK_CUR</code></a> or <code class="docutils literal notranslate">1</code> – current stream position; offset may be negative</li> <li><a class="reference internal" href="os.html#os.SEEK_END" title="os.SEEK_END"><code class="xref py py-data docutils literal notranslate">os.SEEK_END</code></a> or <code class="docutils literal notranslate">2</code> – end of the stream; offset is usually negative</li> </ul> <div class="versionadded"> Added in version 3.1: The <code class="xref py py-data docutils literal notranslate">SEEK_*</code> constants. </div> <div class="versionadded"> Added in version 3.3: Some operating systems could support additional values, like <a class="reference internal" href="os.html#os.SEEK_HOLE" title="os.SEEK_HOLE"><code class="xref py py-const docutils literal notranslate">os.SEEK_HOLE</code></a> or <a class="reference internal" href="os.html#os.SEEK_DATA" title="os.SEEK_DATA"><code class="xref py py-const docutils literal notranslate">os.SEEK_DATA</code></a>. The valid values for a file could depend on it being open in text or binary mode. </div> </dd></dl> <dl class="py method"> <dt class="sig sig-object py" id="io.IOBase.seekable"> seekable()<a class="headerlink" href="#io.IOBase.seekable" title="Link to this definition">¶</a></dt> <dd>Return <code class="docutils literal notranslate">True</code> if the stream supports random access. If <code class="docutils literal notranslate">False</code>, <a class="reference internal" href="#io.IOBase.seek" title="io.IOBase.seek"><code class="xref py py-meth docutils literal notranslate">seek()</code></a>, <a class="reference internal" href="#io.IOBase.tell" title="io.IOBase.tell"><code class="xref py py-meth docutils literal notranslate">tell()</code></a> and <a class="reference internal" href="#io.IOBase.truncate" title="io.IOBase.truncate"><code class="xref py py-meth docutils literal notranslate">truncate()</code></a> will raise <a class="reference internal" href="exceptions.html#OSError" title="OSError"><code class="xref py py-exc docutils literal notranslate">OSError</code></a>. </dd></dl> <dl class="py method"> <dt class="sig sig-object py" id="io.IOBase.tell"> tell()<a class="headerlink" href="#io.IOBase.tell" title="Link to this definition">¶</a></dt> <dd>Return the current stream position. </dd></dl> <dl class="py method"> <dt class="sig sig-object py" id="io.IOBase.truncate"> truncate(size=None, /)<a class="headerlink" href="#io.IOBase.truncate" title="Link to this definition">¶</a></dt> <dd>Resize the stream to the given size in bytes (or the current position if size is not specified). The current stream position isn’t changed. This resizing can extend or reduce the current file size. In case of extension, the contents of the new file area depend on the platform (on most systems, additional bytes are zero-filled). The new file size is returned. <div class="versionchanged"> Changed in version 3.5: Windows will now zero-fill files when extending. </div> </dd></dl> <dl class="py method"> <dt class="sig sig-object py" id="io.IOBase.writable"> writable()<a class="headerlink" href="#io.IOBase.writable" title="Link to this definition">¶</a></dt> <dd>Return <code class="docutils literal notranslate">True</code> if the stream supports writing. If <code class="docutils literal notranslate">False</code>, <code class="xref py py-meth docutils literal notranslate">write()</code> and <a class="reference internal" href="#io.IOBase.truncate" title="io.IOBase.truncate"><code class="xref py py-meth docutils literal notranslate">truncate()</code></a> will raise <a class="reference internal" href="exceptions.html#OSError" title="OSError"><code class="xref py py-exc docutils literal notranslate">OSError</code></a>. </dd></dl> <dl class="py method"> <dt class="sig sig-object py" id="io.IOBase.writelines"> writelines(lines, /)<a class="headerlink" href="#io.IOBase.writelines" title="Link to this definition">¶</a></dt> <dd>Write a list of lines to the stream. Line separators are not added, so it is usual for each of the lines provided to have a line separator at the end. </dd></dl> <dl class="py method"> <dt class="sig sig-object py" id="io.IOBase.__del__"> __del__()<a class="headerlink" href="#io.IOBase.__del__" title="Link to this definition">¶</a></dt> <dd>Prepare for object destruction. <a class="reference internal" href="#io.IOBase" title="io.IOBase"><code class="xref py py-class docutils literal notranslate">IOBase</code></a> provides a default implementation of this method that calls the instance’s <a class="reference internal" href="#io.IOBase.close" title="io.IOBase.close"><code class="xref py py-meth docutils literal notranslate">close()</code></a> method. </dd></dl> </dd></dl> <dl class="py class"> <dt class="sig sig-object py" id="io.RawIOBase"> class io.RawIOBase<a class="headerlink" href="#io.RawIOBase" title="Link to this definition">¶</a></dt> <dd>Base class for raw binary streams. It inherits from <a class="reference internal" href="#io.IOBase" title="io.IOBase"><code class="xref py py-class docutils literal notranslate">IOBase</code></a>. Raw binary streams typically provide low-level access to an underlying OS device or API, and do not try to encapsulate it in high-level primitives (this functionality is done at a higher-level in buffered binary streams and text streams, described later in this page). <a class="reference internal" href="#io.RawIOBase" title="io.RawIOBase"><code class="xref py py-class docutils literal notranslate">RawIOBase</code></a> provides these methods in addition to those from <a class="reference internal" href="#io.IOBase" title="io.IOBase"><code class="xref py py-class docutils literal notranslate">IOBase</code></a>: <dl class="py method"> <dt class="sig sig-object py" id="io.RawIOBase.read"> read(size=-1, /)<a class="headerlink" href="#io.RawIOBase.read" title="Link to this definition">¶</a></dt> <dd>Read up to size bytes from the object and return them. As a convenience, if size is unspecified or -1, all bytes until EOF are returned. Otherwise, only one system call is ever made. Fewer than size bytes may be returned if the operating system call returns fewer than size bytes. If 0 bytes are returned, and size was not 0, this indicates end of file. If the object is in non-blocking mode and no bytes are available, <code class="docutils literal notranslate">None</code> is returned. The default implementation defers to <a class="reference internal" href="#io.RawIOBase.readall" title="io.RawIOBase.readall"><code class="xref py py-meth docutils literal notranslate">readall()</code></a> and <a class="reference internal" href="#io.RawIOBase.readinto" title="io.RawIOBase.readinto"><code class="xref py py-meth docutils literal notranslate">readinto()</code></a>. </dd></dl> <dl class="py method"> <dt class="sig sig-object py" id="io.RawIOBase.readall"> readall()<a class="headerlink" href="#io.RawIOBase.readall" title="Link to this definition">¶</a></dt> <dd>Read and return all the bytes from the stream until EOF, using multiple calls to the stream if necessary. </dd></dl> <dl class="py method"> <dt class="sig sig-object py" id="io.RawIOBase.readinto"> readinto(b, /)<a class="headerlink" href="#io.RawIOBase.readinto" title="Link to this definition">¶</a></dt> <dd>Read bytes into a pre-allocated, writable <a class="reference internal" href="../glossary.html#term-bytes-like-object">bytes-like object</a> b, and return the number of bytes read. For example, b might be a <a class="reference internal" href="stdtypes.html#bytearray" title="bytearray"><code class="xref py py-class docutils literal notranslate">bytearray</code></a>. If the object is in non-blocking mode and no bytes are available, <code class="docutils literal notranslate">None</code> is returned. </dd></dl> <dl class="py method"> <dt class="sig sig-object py" id="io.RawIOBase.write"> write(b, /)<a class="headerlink" href="#io.RawIOBase.write" title="Link to this definition">¶</a></dt> <dd>Write the given <a class="reference internal" href="../glossary.html#term-bytes-like-object">bytes-like object</a>, b, to the underlying raw stream, and return the number of bytes written. This can be less than the length of b in bytes, depending on specifics of the underlying raw stream, and especially if it is in non-blocking mode. <code class="docutils literal notranslate">None</code> is returned if the raw stream is set not to block and no single byte could be readily written to it. The caller may release or mutate b after this method returns, so the implementation should only access b during the method call. </dd></dl> </dd></dl> <dl class="py class"> <dt class="sig sig-object py" id="io.BufferedIOBase"> class io.BufferedIOBase<a class="headerlink" href="#io.BufferedIOBase" title="Link to this definition">¶</a></dt> <dd>Base class for binary streams that support some kind of buffering. It inherits from <a class="reference internal" href="#io.IOBase" title="io.IOBase"><code class="xref py py-class docutils literal notranslate">IOBase</code></a>. The main difference with <a class="reference internal" href="#io.RawIOBase" title="io.RawIOBase"><code class="xref py py-class docutils literal notranslate">RawIOBase</code></a> is that methods <a class="reference internal" href="#io.BufferedIOBase.read" title="io.BufferedIOBase.read"><code class="xref py py-meth docutils literal notranslate">read()</code></a>, <a class="reference internal" href="#io.BufferedIOBase.readinto" title="io.BufferedIOBase.readinto"><code class="xref py py-meth docutils literal notranslate">readinto()</code></a> and <a class="reference internal" href="#io.BufferedIOBase.write" title="io.BufferedIOBase.write"><code class="xref py py-meth docutils literal notranslate">write()</code></a> will try (respectively) to read as much input as requested or to consume all given output, at the expense of making perhaps more than one system call. In addition, those methods can raise <a class="reference internal" href="exceptions.html#BlockingIOError" title="BlockingIOError"><code class="xref py py-exc docutils literal notranslate">BlockingIOError</code></a> if the underlying raw stream is in non-blocking mode and cannot take or give enough data; unlike their <a class="reference internal" href="#io.RawIOBase" title="io.RawIOBase"><code class="xref py py-class docutils literal notranslate">RawIOBase</code></a> counterparts, they will never return <code class="docutils literal notranslate">None</code>. Besides, the <a class="reference internal" href="#io.BufferedIOBase.read" title="io.BufferedIOBase.read"><code class="xref py py-meth docutils literal notranslate">read()</code></a> method does not have a default implementation that defers to <a class="reference internal" href="#io.BufferedIOBase.readinto" title="io.BufferedIOBase.readinto"><code class="xref py py-meth docutils literal notranslate">readinto()</code></a>. A typical <a class="reference internal" href="#io.BufferedIOBase" title="io.BufferedIOBase"><code class="xref py py-class docutils literal notranslate">BufferedIOBase</code></a> implementation should not inherit from a <a class="reference internal" href="#io.RawIOBase" title="io.RawIOBase"><code class="xref py py-class docutils literal notranslate">RawIOBase</code></a> implementation, but wrap one, like <a class="reference internal" href="#io.BufferedWriter" title="io.BufferedWriter"><code class="xref py py-class docutils literal notranslate">BufferedWriter</code></a> and <a class="reference internal" href="#io.BufferedReader" title="io.BufferedReader"><code class="xref py py-class docutils literal notranslate">BufferedReader</code></a> do. <a class="reference internal" href="#io.BufferedIOBase" title="io.BufferedIOBase"><code class="xref py py-class docutils literal notranslate">BufferedIOBase</code></a> provides or overrides these data attributes and methods in addition to those from <a class="reference internal" href="#io.IOBase" title="io.IOBase"><code class="xref py py-class docutils literal notranslate">IOBase</code></a>: <dl class="py attribute"> <dt class="sig sig-object py" id="io.BufferedIOBase.raw"> raw<a class="headerlink" href="#io.BufferedIOBase.raw" title="Link to this definition">¶</a></dt> <dd>The underlying raw stream (a <a class="reference internal" href="#io.RawIOBase" title="io.RawIOBase"><code class="xref py py-class docutils literal notranslate">RawIOBase</code></a> instance) that <a class="reference internal" href="#io.BufferedIOBase" title="io.BufferedIOBase"><code class="xref py py-class docutils literal notranslate">BufferedIOBase</code></a> deals with. This is not part of the <a class="reference internal" href="#io.BufferedIOBase" title="io.BufferedIOBase"><code class="xref py py-class docutils literal notranslate">BufferedIOBase</code></a> API and may not exist on some implementations. </dd></dl> <dl class="py method"> <dt class="sig sig-object py" id="io.BufferedIOBase.detach"> detach()<a class="headerlink" href="#io.BufferedIOBase.detach" title="Link to this definition">¶</a></dt> <dd>Separate the underlying raw stream from the buffer and return it. After the raw stream has been detached, the buffer is in an unusable state. Some buffers, like <a class="reference internal" href="#io.BytesIO" title="io.BytesIO"><code class="xref py py-class docutils literal notranslate">BytesIO</code></a>, do not have the concept of a single raw stream to return from this method. They raise <a class="reference internal" href="#io.UnsupportedOperation" title="io.UnsupportedOperation"><code class="xref py py-exc docutils literal notranslate">UnsupportedOperation</code></a>. <div class="versionadded"> Added in version 3.1. </div> </dd></dl> <dl class="py method"> <dt class="sig sig-object py" id="io.BufferedIOBase.read"> read(size=-1, /)<a class="headerlink" href="#io.BufferedIOBase.read" title="Link to this definition">¶</a></dt> <dd>Read and return up to size bytes. If the argument is omitted, <code class="docutils literal notranslate">None</code>, or negative, data is read and returned until EOF is reached. An empty <a class="reference internal" href="stdtypes.html#bytes" title="bytes"><code class="xref py py-class docutils literal notranslate">bytes</code></a> object is returned if the stream is already at EOF. If the argument is positive, and the underlying raw stream is not interactive, multiple raw reads may be issued to satisfy the byte count (unless EOF is reached first). But for interactive raw streams, at most one raw read will be issued, and a short result does not imply that EOF is imminent. A <a class="reference internal" href="exceptions.html#BlockingIOError" title="BlockingIOError"><code class="xref py py-exc docutils literal notranslate">BlockingIOError</code></a> is raised if the underlying raw stream is in non blocking-mode, and has no data available at the moment. </dd></dl> <dl class="py method"> <dt class="sig sig-object py" id="io.BufferedIOBase.read1"> read1(size=-1, /)<a class="headerlink" href="#io.BufferedIOBase.read1" title="Link to this definition">¶</a></dt> <dd>Read and return up to size bytes, with at most one call to the underlying raw stream’s <a class="reference internal" href="#io.RawIOBase.read" title="io.RawIOBase.read"><code class="xref py py-meth docutils literal notranslate">read()</code></a> (or <a class="reference internal" href="#io.RawIOBase.readinto" title="io.RawIOBase.readinto"><code class="xref py py-meth docutils literal notranslate">readinto()</code></a>) method. This can be useful if you are implementing your own buffering on top of a <a class="reference internal" href="#io.BufferedIOBase" title="io.BufferedIOBase"><code class="xref py py-class docutils literal notranslate">BufferedIOBase</code></a> object. If size is <code class="docutils literal notranslate">-1</code> (the default), an arbitrary number of bytes are returned (more than zero unless EOF is reached). </dd></dl> <dl class="py method"> <dt class="sig sig-object py" id="io.BufferedIOBase.readinto"> readinto(b, /)<a class="headerlink" href="#io.BufferedIOBase.readinto" title="Link to this definition">¶</a></dt> <dd>Read bytes into a pre-allocated, writable <a class="reference internal" href="../glossary.html#term-bytes-like-object">bytes-like object</a> b and return the number of bytes read. For example, b might be a <a class="reference internal" href="stdtypes.html#bytearray" title="bytearray"><code class="xref py py-class docutils literal notranslate">bytearray</code></a>. Like <a class="reference internal" href="#io.BufferedIOBase.read" title="io.BufferedIOBase.read"><code class="xref py py-meth docutils literal notranslate">read()</code></a>, multiple reads may be issued to the underlying raw stream, unless the latter is interactive. A <a class="reference internal" href="exceptions.html#BlockingIOError" title="BlockingIOError"><code class="xref py py-exc docutils literal notranslate">BlockingIOError</code></a> is raised if the underlying raw stream is in non blocking-mode, and has no data available at the moment. </dd></dl> <dl class="py method"> <dt class="sig sig-object py" id="io.BufferedIOBase.readinto1"> readinto1(b, /)<a class="headerlink" href="#io.BufferedIOBase.readinto1" title="Link to this definition">¶</a></dt> <dd>Read bytes into a pre-allocated, writable <a class="reference internal" href="../glossary.html#term-bytes-like-object">bytes-like object</a> b, using at most one call to the underlying raw stream’s <a class="reference internal" href="#io.RawIOBase.read" title="io.RawIOBase.read"><code class="xref py py-meth docutils literal notranslate">read()</code></a> (or <a class="reference internal" href="#io.RawIOBase.readinto" title="io.RawIOBase.readinto"><code class="xref py py-meth docutils literal notranslate">readinto()</code></a>) method. Return the number of bytes read. A <a class="reference internal" href="exceptions.html#BlockingIOError" title="BlockingIOError"><code class="xref py py-exc docutils literal notranslate">BlockingIOError</code></a> is raised if the underlying raw stream is in non blocking-mode, and has no data available at the moment. <div class="versionadded"> Added in version 3.5. </div> </dd></dl> <dl class="py method"> <dt class="sig sig-object py" id="io.BufferedIOBase.write"> write(b, /)<a class="headerlink" href="#io.BufferedIOBase.write" title="Link to this definition">¶</a></dt> <dd>Write the given <a class="reference internal" href="../glossary.html#term-bytes-like-object">bytes-like object</a>, b, and return the number of bytes written (always equal to the length of b in bytes, since if the write fails an <a class="reference internal" href="exceptions.html#OSError" title="OSError"><code class="xref py py-exc docutils literal notranslate">OSError</code></a> will be raised). Depending on the actual implementation, these bytes may be readily written to the underlying stream, or held in a buffer for performance and latency reasons. When in non-blocking mode, a <a class="reference internal" href="exceptions.html#BlockingIOError" title="BlockingIOError"><code class="xref py py-exc docutils literal notranslate">BlockingIOError</code></a> is raised if the data needed to be written to the raw stream but it couldn’t accept all the data without blocking. The caller may release or mutate b after this method returns, so the implementation should only access b during the method call. </dd></dl> </dd></dl> </section> <section id="raw-file-i-o"> <h3>Raw File I/O<a class="headerlink" href="#raw-file-i-o" title="Link to this heading">¶</a></h3> <dl class="py class"> <dt class="sig sig-object py" id="io.FileIO"> class io.FileIO(name, mode='r', closefd=True, opener=None)<a class="headerlink" href="#io.FileIO" title="Link to this definition">¶</a></dt> <dd>A raw binary stream representing an OS-level file containing bytes data. It inherits from <a class="reference internal" href="#io.RawIOBase" title="io.RawIOBase"><code class="xref py py-class docutils literal notranslate">RawIOBase</code></a>. The name can be one of two things: <ul class="simple"> <li>a character string or <a class="reference internal" href="stdtypes.html#bytes" title="bytes"><code class="xref py py-class docutils literal notranslate">bytes</code></a> object representing the path to the file which will be opened. In this case closefd must be <code class="docutils literal notranslate">True</code> (the default) otherwise an error will be raised.</li> <li>an integer representing the number of an existing OS-level file descriptor to which the resulting <a class="reference internal" href="#io.FileIO" title="io.FileIO"><code class="xref py py-class docutils literal notranslate">FileIO</code></a> object will give access. When the FileIO object is closed this fd will be closed as well, unless closefd is set to <code class="docutils literal notranslate">False</code>.</li> </ul> The mode can be <code class="docutils literal notranslate">'r'</code>, <code class="docutils literal notranslate">'w'</code>, <code class="docutils literal notranslate">'x'</code> or <code class="docutils literal notranslate">'a'</code> for reading (default), writing, exclusive creation or appending. The file will be created if it doesn’t exist when opened for writing or appending; it will be truncated when opened for writing. <a class="reference internal" href="exceptions.html#FileExistsError" title="FileExistsError"><code class="xref py py-exc docutils literal notranslate">FileExistsError</code></a> will be raised if it already exists when opened for creating. Opening a file for creating implies writing, so this mode behaves in a similar way to <code class="docutils literal notranslate">'w'</code>. Add a <code class="docutils literal notranslate">'+'</code> to the mode to allow simultaneous reading and writing. The <a class="reference internal" href="#io.RawIOBase.read" title="io.RawIOBase.read"><code class="xref py py-meth docutils literal notranslate">read()</code></a> (when called with a positive argument), <a class="reference internal" href="#io.RawIOBase.readinto" title="io.RawIOBase.readinto"><code class="xref py py-meth docutils literal notranslate">readinto()</code></a> and <a class="reference internal" href="#io.RawIOBase.write" title="io.RawIOBase.write"><code class="xref py py-meth docutils literal notranslate">write()</code></a> methods on this class will only make one system call. A custom opener can be used by passing a callable as opener. The underlying file descriptor for the file object is then obtained by calling opener with (name, flags). opener must return an open file descriptor (passing <a class="reference internal" href="os.html#os.open" title="os.open"><code class="xref py py-mod docutils literal notranslate">os.open</code></a> as opener results in functionality similar to passing <code class="docutils literal notranslate">None</code>). The newly created file is <a class="reference internal" href="os.html#fd-inheritance">non-inheritable</a>. See the <a class="reference internal" href="functions.html#open" title="open"><code class="xref py py-func docutils literal notranslate">open()</code></a> built-in function for examples on using the opener parameter. <div class="versionchanged"> Changed in version 3.3: The opener parameter was added. The <code class="docutils literal notranslate">'x'</code> mode was added. </div> <div class="versionchanged"> Changed in version 3.4: The file is now non-inheritable. </div> <a class="reference internal" href="#io.FileIO" title="io.FileIO"><code class="xref py py-class docutils literal notranslate">FileIO</code></a> provides these data attributes in addition to those from <a class="reference internal" href="#io.RawIOBase" title="io.RawIOBase"><code class="xref py py-class docutils literal notranslate">RawIOBase</code></a> and <a class="reference internal" href="#io.IOBase" title="io.IOBase"><code class="xref py py-class docutils literal notranslate">IOBase</code></a>: <dl class="py attribute"> <dt class="sig sig-object py" id="io.FileIO.mode"> mode<a class="headerlink" href="#io.FileIO.mode" title="Link to this definition">¶</a></dt> <dd>The mode as given in the constructor. </dd></dl> <dl class="py attribute"> <dt class="sig sig-object py" id="io.FileIO.name"> name<a class="headerlink" href="#io.FileIO.name" title="Link to this definition">¶</a></dt> <dd>The file name. This is the file descriptor of the file when no name is given in the constructor. </dd></dl> </dd></dl> </section> <section id="buffered-streams"> <h3>Buffered Streams<a class="headerlink" href="#buffered-streams" title="Link to this heading">¶</a></h3> Buffered I/O streams provide a higher-level interface to an I/O device than raw I/O does. <dl class="py class"> <dt class="sig sig-object py" id="io.BytesIO"> class io.BytesIO(initial_bytes=b'')<a class="headerlink" href="#io.BytesIO" title="Link to this definition">¶</a></dt> <dd>A binary stream using an in-memory bytes buffer. It inherits from <a class="reference internal" href="#io.BufferedIOBase" title="io.BufferedIOBase"><code class="xref py py-class docutils literal notranslate">BufferedIOBase</code></a>. The buffer is discarded when the <a class="reference internal" href="#io.IOBase.close" title="io.IOBase.close"><code class="xref py py-meth docutils literal notranslate">close()</code></a> method is called. The optional argument initial_bytes is a <a class="reference internal" href="../glossary.html#term-bytes-like-object">bytes-like object</a> that contains initial data. <a class="reference internal" href="#io.BytesIO" title="io.BytesIO"><code class="xref py py-class docutils literal notranslate">BytesIO</code></a> provides or overrides these methods in addition to those from <a class="reference internal" href="#io.BufferedIOBase" title="io.BufferedIOBase"><code class="xref py py-class docutils literal notranslate">BufferedIOBase</code></a> and <a class="reference internal" href="#io.IOBase" title="io.IOBase"><code class="xref py py-class docutils literal notranslate">IOBase</code></a>: <dl class="py method"> <dt class="sig sig-object py" id="io.BytesIO.getbuffer"> getbuffer()<a class="headerlink" href="#io.BytesIO.getbuffer" title="Link to this definition">¶</a></dt> <dd>Return a readable and writable view over the contents of the buffer without copying them. Also, mutating the view will transparently update the contents of the buffer: <div class="highlight-python3 notranslate"><div class="highlight"><pre>>>> b = io.BytesIO(b"abcdef") >>> view = b.getbuffer() >>> view[2:4] = b"56" >>> b.getvalue() b'ab56ef' </pre></div> </div> <div class="admonition note"> Note As long as the view exists, the <a class="reference internal" href="#io.BytesIO" title="io.BytesIO"><code class="xref py py-class docutils literal notranslate">BytesIO</code></a> object cannot be resized or closed. </div> <div class="versionadded"> Added in version 3.2. </div> </dd></dl> <dl class="py method"> <dt class="sig sig-object py" id="io.BytesIO.getvalue"> getvalue()<a class="headerlink" href="#io.BytesIO.getvalue" title="Link to this definition">¶</a></dt> <dd>Return <a class="reference internal" href="stdtypes.html#bytes" title="bytes"><code class="xref py py-class docutils literal notranslate">bytes</code></a> containing the entire contents of the buffer. </dd></dl> <dl class="py method"> <dt class="sig sig-object py" id="io.BytesIO.read1"> read1(size=-1, /)<a class="headerlink" href="#io.BytesIO.read1" title="Link to this definition">¶</a></dt> <dd>In <a class="reference internal" href="#io.BytesIO" title="io.BytesIO"><code class="xref py py-class docutils literal notranslate">BytesIO</code></a>, this is the same as <a class="reference internal" href="#io.BufferedIOBase.read" title="io.BufferedIOBase.read"><code class="xref py py-meth docutils literal notranslate">read()</code></a>. <div class="versionchanged"> Changed in version 3.7: The size argument is now optional. </div> </dd></dl> <dl class="py method"> <dt class="sig sig-object py" id="io.BytesIO.readinto1"> readinto1(b, /)<a class="headerlink" href="#io.BytesIO.readinto1" title="Link to this definition">¶</a></dt> <dd>In <a class="reference internal" href="#io.BytesIO" title="io.BytesIO"><code class="xref py py-class docutils literal notranslate">BytesIO</code></a>, this is the same as <a class="reference internal" href="#io.BufferedIOBase.readinto" title="io.BufferedIOBase.readinto"><code class="xref py py-meth docutils literal notranslate">readinto()</code></a>. <div class="versionadded"> Added in version 3.5. </div> </dd></dl> </dd></dl> <dl class="py class"> <dt class="sig sig-object py" id="io.BufferedReader"> class io.BufferedReader(raw, buffer_size=DEFAULT_BUFFER_SIZE)<a class="headerlink" href="#io.BufferedReader" title="Link to this definition">¶</a></dt> <dd>A buffered binary stream providing higher-level access to a readable, non seekable <a class="reference internal" href="#io.RawIOBase" title="io.RawIOBase"><code class="xref py py-class docutils literal notranslate">RawIOBase</code></a> raw binary stream. It inherits from <a class="reference internal" href="#io.BufferedIOBase" title="io.BufferedIOBase"><code class="xref py py-class docutils literal notranslate">BufferedIOBase</code></a>. When reading data from this object, a larger amount of data may be requested from the underlying raw stream, and kept in an internal buffer. The buffered data can then be returned directly on subsequent reads. The constructor creates a <a class="reference internal" href="#io.BufferedReader" title="io.BufferedReader"><code class="xref py py-class docutils literal notranslate">BufferedReader</code></a> for the given readable raw stream and buffer_size. If buffer_size is omitted, <a class="reference internal" href="#io.DEFAULT_BUFFER_SIZE" title="io.DEFAULT_BUFFER_SIZE"><code class="xref py py-data docutils literal notranslate">DEFAULT_BUFFER_SIZE</code></a> is used. <a class="reference internal" href="#io.BufferedReader" title="io.BufferedReader"><code class="xref py py-class docutils literal notranslate">BufferedReader</code></a> provides or overrides these methods in addition to those from <a class="reference internal" href="#io.BufferedIOBase" title="io.BufferedIOBase"><code class="xref py py-class docutils literal notranslate">BufferedIOBase</code></a> and <a class="reference internal" href="#io.IOBase" title="io.IOBase"><code class="xref py py-class docutils literal notranslate">IOBase</code></a>: <dl class="py method"> <dt class="sig sig-object py" id="io.BufferedReader.peek"> peek(size=0, /)<a class="headerlink" href="#io.BufferedReader.peek" title="Link to this definition">¶</a></dt> <dd>Return bytes from the stream without advancing the position. At most one single read on the raw stream is done to satisfy the call. The number of bytes returned may be less or more than requested. </dd></dl> <dl class="py method"> <dt class="sig sig-object py" id="io.BufferedReader.read"> read(size=-1, /)<a class="headerlink" href="#io.BufferedReader.read" title="Link to this definition">¶</a></dt> <dd>Read and return size bytes, or if size is not given or negative, until EOF or if the read call would block in non-blocking mode. </dd></dl> <dl class="py method"> <dt class="sig sig-object py" id="io.BufferedReader.read1"> read1(size=-1, /)<a class="headerlink" href="#io.BufferedReader.read1" title="Link to this definition">¶</a></dt> <dd>Read and return up to size bytes with only one call on the raw stream. If at least one byte is buffered, only buffered bytes are returned. Otherwise, one raw stream read call is made. <div class="versionchanged"> Changed in version 3.7: The size argument is now optional. </div> </dd></dl> </dd></dl> <dl class="py class"> <dt class="sig sig-object py" id="io.BufferedWriter"> class io.BufferedWriter(raw, buffer_size=DEFAULT_BUFFER_SIZE)<a class="headerlink" href="#io.BufferedWriter" title="Link to this definition">¶</a></dt> <dd>A buffered binary stream providing higher-level access to a writeable, non seekable <a class="reference internal" href="#io.RawIOBase" title="io.RawIOBase"><code class="xref py py-class docutils literal notranslate">RawIOBase</code></a> raw binary stream. It inherits from <a class="reference internal" href="#io.BufferedIOBase" title="io.BufferedIOBase"><code class="xref py py-class docutils literal notranslate">BufferedIOBase</code></a>. When writing to this object, data is normally placed into an internal buffer. The buffer will be written out to the underlying <a class="reference internal" href="#io.RawIOBase" title="io.RawIOBase"><code class="xref py py-class docutils literal notranslate">RawIOBase</code></a> object under various conditions, including: <ul class="simple"> <li>when the buffer gets too small for all pending data;</li> <li>when <a class="reference internal" href="#io.BufferedWriter.flush" title="io.BufferedWriter.flush"><code class="xref py py-meth docutils literal notranslate">flush()</code></a> is called;</li> <li>when a <a class="reference internal" href="#io.IOBase.seek" title="io.IOBase.seek"><code class="xref py py-meth docutils literal notranslate">seek()</code></a> is requested (for <a class="reference internal" href="#io.BufferedRandom" title="io.BufferedRandom"><code class="xref py py-class docutils literal notranslate">BufferedRandom</code></a> objects);</li> <li>when the <a class="reference internal" href="#io.BufferedWriter" title="io.BufferedWriter"><code class="xref py py-class docutils literal notranslate">BufferedWriter</code></a> object is closed or destroyed.</li> </ul> The constructor creates a <a class="reference internal" href="#io.BufferedWriter" title="io.BufferedWriter"><code class="xref py py-class docutils literal notranslate">BufferedWriter</code></a> for the given writeable raw stream. If the buffer_size is not given, it defaults to <a class="reference internal" href="#io.DEFAULT_BUFFER_SIZE" title="io.DEFAULT_BUFFER_SIZE"><code class="xref py py-data docutils literal notranslate">DEFAULT_BUFFER_SIZE</code></a>. <a class="reference internal" href="#io.BufferedWriter" title="io.BufferedWriter"><code class="xref py py-class docutils literal notranslate">BufferedWriter</code></a> provides or overrides these methods in addition to those from <a class="reference internal" href="#io.BufferedIOBase" title="io.BufferedIOBase"><code class="xref py py-class docutils literal notranslate">BufferedIOBase</code></a> and <a class="reference internal" href="#io.IOBase" title="io.IOBase"><code class="xref py py-class docutils literal notranslate">IOBase</code></a>: <dl class="py method"> <dt class="sig sig-object py" id="io.BufferedWriter.flush"> flush()<a class="headerlink" href="#io.BufferedWriter.flush" title="Link to this definition">¶</a></dt> <dd>Force bytes held in the buffer into the raw stream. A <a class="reference internal" href="exceptions.html#BlockingIOError" title="BlockingIOError"><code class="xref py py-exc docutils literal notranslate">BlockingIOError</code></a> should be raised if the raw stream blocks. </dd></dl> <dl class="py method"> <dt class="sig sig-object py" id="io.BufferedWriter.write"> write(b, /)<a class="headerlink" href="#io.BufferedWriter.write" title="Link to this definition">¶</a></dt> <dd>Write the <a class="reference internal" href="../glossary.html#term-bytes-like-object">bytes-like object</a>, b, and return the number of bytes written. When in non-blocking mode, a <a class="reference internal" href="exceptions.html#BlockingIOError" title="BlockingIOError"><code class="xref py py-exc docutils literal notranslate">BlockingIOError</code></a> is raised if the buffer needs to be written out but the raw stream blocks. </dd></dl> </dd></dl> <dl class="py class"> <dt class="sig sig-object py" id="io.BufferedRandom"> class io.BufferedRandom(raw, buffer_size=DEFAULT_BUFFER_SIZE)<a class="headerlink" href="#io.BufferedRandom" title="Link to this definition">¶</a></dt> <dd>A buffered binary stream providing higher-level access to a seekable <a class="reference internal" href="#io.RawIOBase" title="io.RawIOBase"><code class="xref py py-class docutils literal notranslate">RawIOBase</code></a> raw binary stream. It inherits from <a class="reference internal" href="#io.BufferedReader" title="io.BufferedReader"><code class="xref py py-class docutils literal notranslate">BufferedReader</code></a> and <a class="reference internal" href="#io.BufferedWriter" title="io.BufferedWriter"><code class="xref py py-class docutils literal notranslate">BufferedWriter</code></a>. The constructor creates a reader and writer for a seekable raw stream, given in the first argument. If the buffer_size is omitted it defaults to <a class="reference internal" href="#io.DEFAULT_BUFFER_SIZE" title="io.DEFAULT_BUFFER_SIZE"><code class="xref py py-data docutils literal notranslate">DEFAULT_BUFFER_SIZE</code></a>. <a class="reference internal" href="#io.BufferedRandom" title="io.BufferedRandom"><code class="xref py py-class docutils literal notranslate">BufferedRandom</code></a> is capable of anything <a class="reference internal" href="#io.BufferedReader" title="io.BufferedReader"><code class="xref py py-class docutils literal notranslate">BufferedReader</code></a> or <a class="reference internal" href="#io.BufferedWriter" title="io.BufferedWriter"><code class="xref py py-class docutils literal notranslate">BufferedWriter</code></a> can do. In addition, <a class="reference internal" href="#io.IOBase.seek" title="io.IOBase.seek"><code class="xref py py-meth docutils literal notranslate">seek()</code></a> and <a class="reference internal" href="#io.IOBase.tell" title="io.IOBase.tell"><code class="xref py py-meth docutils literal notranslate">tell()</code></a> are guaranteed to be implemented. </dd></dl> <dl class="py class"> <dt class="sig sig-object py" id="io.BufferedRWPair"> class io.BufferedRWPair(reader, writer, buffer_size=DEFAULT_BUFFER_SIZE, /)<a class="headerlink" href="#io.BufferedRWPair" title="Link to this definition">¶</a></dt> <dd>A buffered binary stream providing higher-level access to two non seekable <a class="reference internal" href="#io.RawIOBase" title="io.RawIOBase"><code class="xref py py-class docutils literal notranslate">RawIOBase</code></a> raw binary streams—one readable, the other writeable. It inherits from <a class="reference internal" href="#io.BufferedIOBase" title="io.BufferedIOBase"><code class="xref py py-class docutils literal notranslate">BufferedIOBase</code></a>. reader and writer are <a class="reference internal" href="#io.RawIOBase" title="io.RawIOBase"><code class="xref py py-class docutils literal notranslate">RawIOBase</code></a> objects that are readable and writeable respectively. If the buffer_size is omitted it defaults to <a class="reference internal" href="#io.DEFAULT_BUFFER_SIZE" title="io.DEFAULT_BUFFER_SIZE"><code class="xref py py-data docutils literal notranslate">DEFAULT_BUFFER_SIZE</code></a>. <a class="reference internal" href="#io.BufferedRWPair" title="io.BufferedRWPair"><code class="xref py py-class docutils literal notranslate">BufferedRWPair</code></a> implements all of <a class="reference internal" href="#io.BufferedIOBase" title="io.BufferedIOBase"><code class="xref py py-class docutils literal notranslate">BufferedIOBase</code></a>'s methods except for <a class="reference internal" href="#io.BufferedIOBase.detach" title="io.BufferedIOBase.detach"><code class="xref py py-meth docutils literal notranslate">detach()</code></a>, which raises <a class="reference internal" href="#io.UnsupportedOperation" title="io.UnsupportedOperation"><code class="xref py py-exc docutils literal notranslate">UnsupportedOperation</code></a>. <div class="admonition warning"> Warning <a class="reference internal" href="#io.BufferedRWPair" title="io.BufferedRWPair"><code class="xref py py-class docutils literal notranslate">BufferedRWPair</code></a> does not attempt to synchronize accesses to its underlying raw streams. You should not pass it the same object as reader and writer; use <a class="reference internal" href="#io.BufferedRandom" title="io.BufferedRandom"><code class="xref py py-class docutils literal notranslate">BufferedRandom</code></a> instead. </div> </dd></dl> </section> <section id="id1"> <h3>Text I/O<a class="headerlink" href="#id1" title="Link to this heading">¶</a></h3> <dl class="py class"> <dt class="sig sig-object py" id="io.TextIOBase"> class io.TextIOBase<a class="headerlink" href="#io.TextIOBase" title="Link to this definition">¶</a></dt> <dd>Base class for text streams. This class provides a character and line based interface to stream I/O. It inherits from <a class="reference internal" href="#io.IOBase" title="io.IOBase"><code class="xref py py-class docutils literal notranslate">IOBase</code></a>. <a class="reference internal" href="#io.TextIOBase" title="io.TextIOBase"><code class="xref py py-class docutils literal notranslate">TextIOBase</code></a> provides or overrides these data attributes and methods in addition to those from <a class="reference internal" href="#io.IOBase" title="io.IOBase"><code class="xref py py-class docutils literal notranslate">IOBase</code></a>: <dl class="py attribute"> <dt class="sig sig-object py" id="io.TextIOBase.encoding"> encoding<a class="headerlink" href="#io.TextIOBase.encoding" title="Link to this definition">¶</a></dt> <dd>The name of the encoding used to decode the stream’s bytes into strings, and to encode strings into bytes. </dd></dl> <dl class="py attribute"> <dt class="sig sig-object py" id="io.TextIOBase.errors"> errors<a class="headerlink" href="#io.TextIOBase.errors" title="Link to this definition">¶</a></dt> <dd>The error setting of the decoder or encoder. </dd></dl> <dl class="py attribute"> <dt class="sig sig-object py" id="io.TextIOBase.newlines"> newlines<a class="headerlink" href="#io.TextIOBase.newlines" title="Link to this definition">¶</a></dt> <dd>A string, a tuple of strings, or <code class="docutils literal notranslate">None</code>, indicating the newlines translated so far. Depending on the implementation and the initial constructor flags, this may not be available. </dd></dl> <dl class="py attribute"> <dt class="sig sig-object py" id="io.TextIOBase.buffer"> buffer<a class="headerlink" href="#io.TextIOBase.buffer" title="Link to this definition">¶</a></dt> <dd>The underlying binary buffer (a <a class="reference internal" href="#io.BufferedIOBase" title="io.BufferedIOBase"><code class="xref py py-class docutils literal notranslate">BufferedIOBase</code></a> instance) that <a class="reference internal" href="#io.TextIOBase" title="io.TextIOBase"><code class="xref py py-class docutils literal notranslate">TextIOBase</code></a> deals with. This is not part of the <a class="reference internal" href="#io.TextIOBase" title="io.TextIOBase"><code class="xref py py-class docutils literal notranslate">TextIOBase</code></a> API and may not exist in some implementations. </dd></dl> <dl class="py method"> <dt class="sig sig-object py" id="io.TextIOBase.detach"> detach()<a class="headerlink" href="#io.TextIOBase.detach" title="Link to this definition">¶</a></dt> <dd>Separate the underlying binary buffer from the <a class="reference internal" href="#io.TextIOBase" title="io.TextIOBase"><code class="xref py py-class docutils literal notranslate">TextIOBase</code></a> and return it. After the underlying buffer has been detached, the <a class="reference internal" href="#io.TextIOBase" title="io.TextIOBase"><code class="xref py py-class docutils literal notranslate">TextIOBase</code></a> is in an unusable state. Some <a class="reference internal" href="#io.TextIOBase" title="io.TextIOBase"><code class="xref py py-class docutils literal notranslate">TextIOBase</code></a> implementations, like <a class="reference internal" href="#io.StringIO" title="io.StringIO"><code class="xref py py-class docutils literal notranslate">StringIO</code></a>, may not have the concept of an underlying buffer and calling this method will raise <a class="reference internal" href="#io.UnsupportedOperation" title="io.UnsupportedOperation"><code class="xref py py-exc docutils literal notranslate">UnsupportedOperation</code></a>. <div class="versionadded"> Added in version 3.1. </div> </dd></dl> <dl class="py method"> <dt class="sig sig-object py" id="io.TextIOBase.read"> read(size=-1, /)<a class="headerlink" href="#io.TextIOBase.read" title="Link to this definition">¶</a></dt> <dd>Read and return at most size characters from the stream as a single <a class="reference internal" href="stdtypes.html#str" title="str"><code class="xref py py-class docutils literal notranslate">str</code></a>. If size is negative or <code class="docutils literal notranslate">None</code>, reads until EOF. </dd></dl> <dl class="py method"> <dt class="sig sig-object py" id="io.TextIOBase.readline"> readline(size=-1, /)<a class="headerlink" href="#io.TextIOBase.readline" title="Link to this definition">¶</a></dt> <dd>Read until newline or EOF and return a single <a class="reference internal" href="stdtypes.html#str" title="str"><code class="xref py py-class docutils literal notranslate">str</code></a>. If the stream is already at EOF, an empty string is returned. If size is specified, at most size characters will be read. </dd></dl> <dl class="py method"> <dt class="sig sig-object py" id="io.TextIOBase.seek"> seek(offset, whence=SEEK_SET, /)<a class="headerlink" href="#io.TextIOBase.seek" title="Link to this definition">¶</a></dt> <dd>Change the stream position to the given offset. Behaviour depends on the whence parameter. The default value for whence is <code class="xref py py-data docutils literal notranslate">SEEK_SET</code>. <ul class="simple"> <li><code class="xref py py-data docutils literal notranslate">SEEK_SET</code> or <code class="docutils literal notranslate">0</code>: seek from the start of the stream (the default); offset must either be a number returned by <a class="reference internal" href="#io.TextIOBase.tell" title="io.TextIOBase.tell"><code class="xref py py-meth docutils literal notranslate">TextIOBase.tell()</code></a>, or zero. Any other offset value produces undefined behaviour.</li> <li><code class="xref py py-data docutils literal notranslate">SEEK_CUR</code> or <code class="docutils literal notranslate">1</code>: “seek” to the current position; offset must be zero, which is a no-operation (all other values are unsupported).</li> <li><code class="xref py py-data docutils literal notranslate">SEEK_END</code> or <code class="docutils literal notranslate">2</code>: seek to the end of the stream; offset must be zero (all other values are unsupported).</li> </ul> Return the new absolute position as an opaque number. <div class="versionadded"> Added in version 3.1: The <code class="xref py py-data docutils literal notranslate">SEEK_*</code> constants. </div> </dd></dl> <dl class="py method"> <dt class="sig sig-object py" id="io.TextIOBase.tell"> tell()<a class="headerlink" href="#io.TextIOBase.tell" title="Link to this definition">¶</a></dt> <dd>Return the current stream position as an opaque number. The number does not usually represent a number of bytes in the underlying binary storage. </dd></dl> <dl class="py method"> <dt class="sig sig-object py" id="io.TextIOBase.write"> write(s, /)<a class="headerlink" href="#io.TextIOBase.write" title="Link to this definition">¶</a></dt> <dd>Write the string s to the stream and return the number of characters written. </dd></dl> </dd></dl> <dl class="py class"> <dt class="sig sig-object py" id="io.TextIOWrapper"> class io.TextIOWrapper(buffer, encoding=None, errors=None, newline=None, line_buffering=False, write_through=False)<a class="headerlink" href="#io.TextIOWrapper" title="Link to this definition">¶</a></dt> <dd>A buffered text stream providing higher-level access to a <a class="reference internal" href="#io.BufferedIOBase" title="io.BufferedIOBase"><code class="xref py py-class docutils literal notranslate">BufferedIOBase</code></a> buffered binary stream. It inherits from <a class="reference internal" href="#io.TextIOBase" title="io.TextIOBase"><code class="xref py py-class docutils literal notranslate">TextIOBase</code></a>. encoding gives the name of the encoding that the stream will be decoded or encoded with. It defaults to <a class="reference internal" href="locale.html#locale.getencoding" title="locale.getencoding"><code class="xref py py-func docutils literal notranslate">locale.getencoding()</code></a>. <code class="docutils literal notranslate">encoding="locale"</code> can be used to specify the current locale’s encoding explicitly. See <a class="reference internal" href="#io-text-encoding">Text Encoding</a> for more information. errors is an optional string that specifies how encoding and decoding errors are to be handled. Pass <code class="docutils literal notranslate">'strict'</code> to raise a <a class="reference internal" href="exceptions.html#ValueError" title="ValueError"><code class="xref py py-exc docutils literal notranslate">ValueError</code></a> exception if there is an encoding error (the default of <code class="docutils literal notranslate">None</code> has the same effect), or pass <code class="docutils literal notranslate">'ignore'</code> to ignore errors. (Note that ignoring encoding errors can lead to data loss.) <code class="docutils literal notranslate">'replace'</code> causes a replacement marker (such as <code class="docutils literal notranslate">'?'</code>) to be inserted where there is malformed data. <code class="docutils literal notranslate">'backslashreplace'</code> causes malformed data to be replaced by a backslashed escape sequence. When writing, <code class="docutils literal notranslate">'xmlcharrefreplace'</code> (replace with the appropriate XML character reference) or <code class="docutils literal notranslate">'namereplace'</code> (replace with <code class="docutils literal notranslate">\N{...}</code> escape sequences) can be used. Any other error handling name that has been registered with <a class="reference internal" href="codecs.html#codecs.register_error" title="codecs.register_error"><code class="xref py py-func docutils literal notranslate">codecs.register_error()</code></a> is also valid. newline controls how line endings are handled. It can be <code class="docutils literal notranslate">None</code>, <code class="docutils literal notranslate">''</code>, <code class="docutils literal notranslate">'\n'</code>, <code class="docutils literal notranslate">'\r'</code>, and <code class="docutils literal notranslate">'\r\n'</code>. It works as follows: <ul class="simple"> <li>When reading input from the stream, if newline is <code class="docutils literal notranslate">None</code>, <a class="reference internal" href="../glossary.html#term-universal-newlines">universal newlines</a> mode is enabled. Lines in the input can end in <code class="docutils literal notranslate">'\n'</code>, <code class="docutils literal notranslate">'\r'</code>, or <code class="docutils literal notranslate">'\r\n'</code>, and these are translated into <code class="docutils literal notranslate">'\n'</code> before being returned to the caller. If newline is <code class="docutils literal notranslate">''</code>, universal newlines mode is enabled, but line endings are returned to the caller untranslated. If newline has any of the other legal values, input lines are only terminated by the given string, and the line ending is returned to the caller untranslated.</li> <li>When writing output to the stream, if newline is <code class="docutils literal notranslate">None</code>, any <code class="docutils literal notranslate">'\n'</code> characters written are translated to the system default line separator, <a class="reference internal" href="os.html#os.linesep" title="os.linesep"><code class="xref py py-data docutils literal notranslate">os.linesep</code></a>. If newline is <code class="docutils literal notranslate">''</code> or <code class="docutils literal notranslate">'\n'</code>, no translation takes place. If newline is any of the other legal values, any <code class="docutils literal notranslate">'\n'</code> characters written are translated to the given string.</li> </ul> If line_buffering is <code class="docutils literal notranslate">True</code>, <a class="reference internal" href="#io.IOBase.flush" title="io.IOBase.flush"><code class="xref py py-meth docutils literal notranslate">flush()</code></a> is implied when a call to write contains a newline character or a carriage return. If write_through is <code class="docutils literal notranslate">True</code>, calls to <a class="reference internal" href="#io.BufferedIOBase.write" title="io.BufferedIOBase.write"><code class="xref py py-meth docutils literal notranslate">write()</code></a> are guaranteed not to be buffered: any data written on the <a class="reference internal" href="#io.TextIOWrapper" title="io.TextIOWrapper"><code class="xref py py-class docutils literal notranslate">TextIOWrapper</code></a> object is immediately handled to its underlying binary buffer. <div class="versionchanged"> Changed in version 3.3: The write_through argument has been added. </div> <div class="versionchanged"> Changed in version 3.3: The default encoding is now <code class="docutils literal notranslate">locale.getpreferredencoding(False)</code> instead of <code class="docutils literal notranslate">locale.getpreferredencoding()</code>. Don’t change temporary the locale encoding using <a class="reference internal" href="locale.html#locale.setlocale" title="locale.setlocale"><code class="xref py py-func docutils literal notranslate">locale.setlocale()</code></a>, use the current locale encoding instead of the user preferred encoding. </div> <div class="versionchanged"> Changed in version 3.10: The encoding argument now supports the <code class="docutils literal notranslate">"locale"</code> dummy encoding name. </div> <a class="reference internal" href="#io.TextIOWrapper" title="io.TextIOWrapper"><code class="xref py py-class docutils literal notranslate">TextIOWrapper</code></a> provides these data attributes and methods in addition to those from <a class="reference internal" href="#io.TextIOBase" title="io.TextIOBase"><code class="xref py py-class docutils literal notranslate">TextIOBase</code></a> and <a class="reference internal" href="#io.IOBase" title="io.IOBase"><code class="xref py py-class docutils literal notranslate">IOBase</code></a>: <dl class="py attribute"> <dt class="sig sig-object py" id="io.TextIOWrapper.line_buffering"> line_buffering<a class="headerlink" href="#io.TextIOWrapper.line_buffering" title="Link to this definition">¶</a></dt> <dd>Whether line buffering is enabled. </dd></dl> <dl class="py attribute"> <dt class="sig sig-object py" id="io.TextIOWrapper.write_through"> write_through<a class="headerlink" href="#io.TextIOWrapper.write_through" title="Link to this definition">¶</a></dt> <dd>Whether writes are passed immediately to the underlying binary buffer. <div class="versionadded"> Added in version 3.7. </div> </dd></dl> <dl class="py method"> <dt class="sig sig-object py" id="io.TextIOWrapper.reconfigure"> reconfigure(*, encoding=None, errors=None, newline=None, line_buffering=None, write_through=None)<a class="headerlink" href="#io.TextIOWrapper.reconfigure" title="Link to this definition">¶</a></dt> <dd>Reconfigure this text stream using new settings for encoding, errors, newline, line_buffering and write_through. Parameters not specified keep current settings, except <code class="docutils literal notranslate">errors='strict'</code> is used when encoding is specified but errors is not specified. It is not possible to change the encoding or newline if some data has already been read from the stream. On the other hand, changing encoding after write is possible. This method does an implicit stream flush before setting the new parameters. <div class="versionadded"> Added in version 3.7. </div> <div class="versionchanged"> Changed in version 3.11: The method supports <code class="docutils literal notranslate">encoding="locale"</code> option. </div> </dd></dl> <dl class="py method"> <dt class="sig sig-object py" id="io.TextIOWrapper.seek"> seek(cookie, whence=os.SEEK_SET, /)<a class="headerlink" href="#io.TextIOWrapper.seek" title="Link to this definition">¶</a></dt> <dd>Set the stream position. Return the new stream position as an <a class="reference internal" href="functions.html#int" title="int"><code class="xref py py-class docutils literal notranslate">int</code></a>. Four operations are supported, given by the following argument combinations: <ul class="simple"> <li><code class="docutils literal notranslate">seek(0, SEEK_SET)</code>: Rewind to the start of the stream.</li> <li><code class="docutils literal notranslate">seek(cookie, SEEK_SET)</code>: Restore a previous position; cookie must be a number returned by <a class="reference internal" href="#io.TextIOWrapper.tell" title="io.TextIOWrapper.tell"><code class="xref py py-meth docutils literal notranslate">tell()</code></a>.</li> <li><code class="docutils literal notranslate">seek(0, SEEK_END)</code>: Fast-forward to the end of the stream.</li> <li><code class="docutils literal notranslate">seek(0, SEEK_CUR)</code>: Leave the current stream position unchanged.</li> </ul> Any other argument combinations are invalid, and may raise exceptions. <div class="admonition seealso"> See also <a class="reference internal" href="os.html#os.SEEK_SET" title="os.SEEK_SET"><code class="xref py py-data docutils literal notranslate">os.SEEK_SET</code></a>, <a class="reference internal" href="os.html#os.SEEK_CUR" title="os.SEEK_CUR"><code class="xref py py-data docutils literal notranslate">os.SEEK_CUR</code></a>, and <a class="reference internal" href="os.html#os.SEEK_END" title="os.SEEK_END"><code class="xref py py-data docutils literal notranslate">os.SEEK_END</code></a>. </div> </dd></dl> <dl class="py method"> <dt class="sig sig-object py" id="io.TextIOWrapper.tell"> tell()<a class="headerlink" href="#io.TextIOWrapper.tell" title="Link to this definition">¶</a></dt> <dd>Return the stream position as an opaque number. The return value of <code class="xref py py-meth docutils literal notranslate">tell()</code> can be given as input to <a class="reference internal" href="#io.TextIOWrapper.seek" title="io.TextIOWrapper.seek"><code class="xref py py-meth docutils literal notranslate">seek()</code></a>, to restore a previous stream position. </dd></dl> </dd></dl> <dl class="py class"> <dt class="sig sig-object py" id="io.StringIO"> class io.StringIO(initial_value='', newline='\n')<a class="headerlink" href="#io.StringIO" title="Link to this definition">¶</a></dt> <dd>A text stream using an in-memory text buffer. It inherits from <a class="reference internal" href="#io.TextIOBase" title="io.TextIOBase"><code class="xref py py-class docutils literal notranslate">TextIOBase</code></a>. The text buffer is discarded when the <a class="reference internal" href="#io.IOBase.close" title="io.IOBase.close"><code class="xref py py-meth docutils literal notranslate">close()</code></a> method is called. The initial value of the buffer can be set by providing initial_value. If newline translation is enabled, newlines will be encoded as if by <a class="reference internal" href="#io.TextIOBase.write" title="io.TextIOBase.write"><code class="xref py py-meth docutils literal notranslate">write()</code></a>. The stream is positioned at the start of the buffer which emulates opening an existing file in a <code class="docutils literal notranslate">w+</code> mode, making it ready for an immediate write from the beginning or for a write that would overwrite the initial value. To emulate opening a file in an <code class="docutils literal notranslate">a+</code> mode ready for appending, use <code class="docutils literal notranslate">f.seek(0, io.SEEK_END)</code> to reposition the stream at the end of the buffer. The newline argument works like that of <a class="reference internal" href="#io.TextIOWrapper" title="io.TextIOWrapper"><code class="xref py py-class docutils literal notranslate">TextIOWrapper</code></a>, except that when writing output to the stream, if newline is <code class="docutils literal notranslate">None</code>, newlines are written as <code class="docutils literal notranslate">\n</code> on all platforms. <a class="reference internal" href="#io.StringIO" title="io.StringIO"><code class="xref py py-class docutils literal notranslate">StringIO</code></a> provides this method in addition to those from <a class="reference internal" href="#io.TextIOBase" title="io.TextIOBase"><code class="xref py py-class docutils literal notranslate">TextIOBase</code></a> and <a class="reference internal" href="#io.IOBase" title="io.IOBase"><code class="xref py py-class docutils literal notranslate">IOBase</code></a>: <dl class="py method"> <dt class="sig sig-object py" id="io.StringIO.getvalue"> getvalue()<a class="headerlink" href="#io.StringIO.getvalue" title="Link to this definition">¶</a></dt> <dd>Return a <a class="reference internal" href="stdtypes.html#str" title="str"><code class="xref py py-class docutils literal notranslate">str</code></a> containing the entire contents of the buffer. Newlines are decoded as if by <a class="reference internal" href="#io.TextIOBase.read" title="io.TextIOBase.read"><code class="xref py py-meth docutils literal notranslate">read()</code></a>, although the stream position is not changed. </dd></dl> Example usage: <div class="highlight-python3 notranslate"><div class="highlight"><pre>import io output = io.StringIO() output.write('First line.\n') print('Second line.', file=output) # Retrieve file contents -- this will be # 'First line.\nSecond line.\n' contents = output.getvalue() # Close object and discard memory buffer -- # .getvalue() will now raise an exception. output.close() </pre></div> </div> </dd></dl> <dl class="py class" id="index-5"> <dt class="sig sig-object py" id="io.IncrementalNewlineDecoder"> class io.IncrementalNewlineDecoder<a class="headerlink" href="#io.IncrementalNewlineDecoder" title="Link to this definition">¶</a></dt> <dd>A helper codec that decodes newlines for <a class="reference internal" href="../glossary.html#term-universal-newlines">universal newlines</a> mode. It inherits from <a class="reference internal" href="codecs.html#codecs.IncrementalDecoder" title="codecs.IncrementalDecoder"><code class="xref py py-class docutils literal notranslate">codecs.IncrementalDecoder</code></a>. </dd></dl> </section> </section> <section id="performance"> <h2>Performance<a class="headerlink" href="#performance" title="Link to this heading">¶</a></h2> This section discusses the performance of the provided concrete I/O implementations. <section id="id2"> <h3>Binary I/O<a class="headerlink" href="#id2" title="Link to this heading">¶</a></h3> By reading and writing only large chunks of data even when the user asks for a single byte, buffered I/O hides any inefficiency in calling and executing the operating system’s unbuffered I/O routines. The gain depends on the OS and the kind of I/O which is performed. For example, on some modern OSes such as Linux, unbuffered disk I/O can be as fast as buffered I/O. The bottom line, however, is that buffered I/O offers predictable performance regardless of the platform and the backing device. Therefore, it is almost always preferable to use buffered I/O rather than unbuffered I/O for binary data. </section> <section id="id3"> <h3>Text I/O<a class="headerlink" href="#id3" title="Link to this heading">¶</a></h3> Text I/O over a binary storage (such as a file) is significantly slower than binary I/O over the same storage, because it requires conversions between unicode and binary data using a character codec. This can become noticeable handling huge amounts of text data like large log files. Also, <a class="reference internal" href="#io.TextIOBase.tell" title="io.TextIOBase.tell"><code class="xref py py-meth docutils literal notranslate">tell()</code></a> and <a class="reference internal" href="#io.TextIOBase.seek" title="io.TextIOBase.seek"><code class="xref py py-meth docutils literal notranslate">seek()</code></a> are both quite slow due to the reconstruction algorithm used. <a class="reference internal" href="#io.StringIO" title="io.StringIO"><code class="xref py py-class docutils literal notranslate">StringIO</code></a>, however, is a native in-memory unicode container and will exhibit similar speed to <a class="reference internal" href="#io.BytesIO" title="io.BytesIO"><code class="xref py py-class docutils literal notranslate">BytesIO</code></a>. </section> <section id="multi-threading"> <h3>Multi-threading<a class="headerlink" href="#multi-threading" title="Link to this heading">¶</a></h3> <a class="reference internal" href="#io.FileIO" title="io.FileIO"><code class="xref py py-class docutils literal notranslate">FileIO</code></a> objects are thread-safe to the extent that the operating system calls (such as <a class="manpage reference external" href="https://manpages.debian.org/read(2)">read(2)</a> under Unix) they wrap are thread-safe too. Binary buffered objects (instances of <a class="reference internal" href="#io.BufferedReader" title="io.BufferedReader"><code class="xref py py-class docutils literal notranslate">BufferedReader</code></a>, <a class="reference internal" href="#io.BufferedWriter" title="io.BufferedWriter"><code class="xref py py-class docutils literal notranslate">BufferedWriter</code></a>, <a class="reference internal" href="#io.BufferedRandom" title="io.BufferedRandom"><code class="xref py py-class docutils literal notranslate">BufferedRandom</code></a> and <a class="reference internal" href="#io.BufferedRWPair" title="io.BufferedRWPair"><code class="xref py py-class docutils literal notranslate">BufferedRWPair</code></a>) protect their internal structures using a lock; it is therefore safe to call them from multiple threads at once. <a class="reference internal" href="#io.TextIOWrapper" title="io.TextIOWrapper"><code class="xref py py-class docutils literal notranslate">TextIOWrapper</code></a> objects are not thread-safe. </section> <section id="reentrancy"> <h3>Reentrancy<a class="headerlink" href="#reentrancy" title="Link to this heading">¶</a></h3> Binary buffered objects (instances of <a class="reference internal" href="#io.BufferedReader" title="io.BufferedReader"><code class="xref py py-class docutils literal notranslate">BufferedReader</code></a>, <a class="reference internal" href="#io.BufferedWriter" title="io.BufferedWriter"><code class="xref py py-class docutils literal notranslate">BufferedWriter</code></a>, <a class="reference internal" href="#io.BufferedRandom" title="io.BufferedRandom"><code class="xref py py-class docutils literal notranslate">BufferedRandom</code></a> and <a class="reference internal" href="#io.BufferedRWPair" title="io.BufferedRWPair"><code class="xref py py-class docutils literal notranslate">BufferedRWPair</code></a>) are not reentrant. While reentrant calls will not happen in normal situations, they can arise from doing I/O in a <a class="reference internal" href="signal.html#module-signal" title="signal: Set handlers for asynchronous events."><code class="xref py py-mod docutils literal notranslate">signal</code></a> handler. If a thread tries to re-enter a buffered object which it is already accessing, a <a class="reference internal" href="exceptions.html#RuntimeError" title="RuntimeError"><code class="xref py py-exc docutils literal notranslate">RuntimeError</code></a> is raised. Note this doesn’t prohibit a different thread from entering the buffered object. The above implicitly extends to text files, since the <a class="reference internal" href="functions.html#open" title="open"><code class="xref py py-func docutils literal notranslate">open()</code></a> function will wrap a buffered object inside a <a class="reference internal" href="#io.TextIOWrapper" title="io.TextIOWrapper"><code class="xref py py-class docutils literal notranslate">TextIOWrapper</code></a>. This includes standard streams and therefore affects the built-in <a class="reference internal" href="functions.html#print" title="print"><code class="xref py py-func docutils literal notranslate">print()</code></a> function as well. </section> </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="#"><code class="xref py py-mod docutils literal notranslate">io</code> — Core tools for working with streams</a><ul> <li><a class="reference internal" href="#overview">Overview</a><ul> <li><a class="reference internal" href="#text-i-o">Text I/O</a></li> <li><a class="reference internal" href="#binary-i-o">Binary I/O</a></li> <li><a class="reference internal" href="#raw-i-o">Raw I/O</a></li> </ul> </li> <li><a class="reference internal" href="#text-encoding">Text Encoding</a><ul> <li><a class="reference internal" href="#opt-in-encodingwarning">Opt-in EncodingWarning</a></li> </ul> </li> <li><a class="reference internal" href="#high-level-module-interface">High-level Module Interface</a><ul> <li><a class="reference internal" href="#io.DEFAULT_BUFFER_SIZE"><code class="docutils literal notranslate">DEFAULT_BUFFER_SIZE</code></a></li> <li><a class="reference internal" href="#io.open"><code class="docutils literal notranslate">open()</code></a></li> <li><a class="reference internal" href="#io.open_code"><code class="docutils literal notranslate">open_code()</code></a></li> <li><a class="reference internal" href="#io.text_encoding"><code class="docutils literal notranslate">text_encoding()</code></a></li> <li><a class="reference internal" href="#io.BlockingIOError"><code class="docutils literal notranslate">BlockingIOError</code></a></li> <li><a class="reference internal" href="#io.UnsupportedOperation"><code class="docutils literal notranslate">UnsupportedOperation</code></a></li> </ul> </li> <li><a class="reference internal" href="#class-hierarchy">Class hierarchy</a><ul> <li><a class="reference internal" href="#i-o-base-classes">I/O Base Classes</a><ul> <li><a class="reference internal" href="#io.IOBase"><code class="docutils literal notranslate">IOBase</code></a><ul> <li><a class="reference internal" href="#io.IOBase.close"><code class="docutils literal notranslate">close()</code></a></li> <li><a class="reference internal" href="#io.IOBase.closed"><code class="docutils literal notranslate">closed</code></a></li> <li><a class="reference internal" href="#io.IOBase.fileno"><code class="docutils literal notranslate">fileno()</code></a></li> <li><a class="reference internal" href="#io.IOBase.flush"><code class="docutils literal notranslate">flush()</code></a></li> <li><a class="reference internal" href="#io.IOBase.isatty"><code class="docutils literal notranslate">isatty()</code></a></li> <li><a class="reference internal" href="#io.IOBase.readable"><code class="docutils literal notranslate">readable()</code></a></li> <li><a class="reference internal" href="#io.IOBase.readline"><code class="docutils literal notranslate">readline()</code></a></li> <li><a class="reference internal" href="#io.IOBase.readlines"><code class="docutils literal notranslate">readlines()</code></a></li> <li><a class="reference internal" href="#io.IOBase.seek"><code class="docutils literal notranslate">seek()</code></a></li> <li><a class="reference internal" href="#io.IOBase.seekable"><code class="docutils literal notranslate">seekable()</code></a></li> <li><a class="reference internal" href="#io.IOBase.tell"><code class="docutils literal notranslate">tell()</code></a></li> <li><a class="reference internal" href="#io.IOBase.truncate"><code class="docutils literal notranslate">truncate()</code></a></li> <li><a class="reference internal" href="#io.IOBase.writable"><code class="docutils literal notranslate">writable()</code></a></li> <li><a class="reference internal" href="#io.IOBase.writelines"><code class="docutils literal notranslate">writelines()</code></a></li> <li><a class="reference internal" href="#io.IOBase.__del__"><code class="docutils literal notranslate">__del__()</code></a></li> </ul> </li> <li><a class="reference internal" href="#io.RawIOBase"><code class="docutils literal notranslate">RawIOBase</code></a><ul> <li><a class="reference internal" href="#io.RawIOBase.read"><code class="docutils literal notranslate">read()</code></a></li> <li><a class="reference internal" href="#io.RawIOBase.readall"><code class="docutils literal notranslate">readall()</code></a></li> <li><a class="reference internal" href="#io.RawIOBase.readinto"><code class="docutils literal notranslate">readinto()</code></a></li> <li><a class="reference internal" href="#io.RawIOBase.write"><code class="docutils literal notranslate">write()</code></a></li> </ul> </li> <li><a class="reference internal" href="#io.BufferedIOBase"><code class="docutils literal notranslate">BufferedIOBase</code></a><ul> <li><a class="reference internal" href="#io.BufferedIOBase.raw"><code class="docutils literal notranslate">raw</code></a></li> <li><a class="reference internal" href="#io.BufferedIOBase.detach"><code class="docutils literal notranslate">detach()</code></a></li> <li><a class="reference internal" href="#io.BufferedIOBase.read"><code class="docutils literal notranslate">read()</code></a></li> <li><a class="reference internal" href="#io.BufferedIOBase.read1"><code class="docutils literal notranslate">read1()</code></a></li> <li><a class="reference internal" href="#io.BufferedIOBase.readinto"><code class="docutils literal notranslate">readinto()</code></a></li> <li><a class="reference internal" href="#io.BufferedIOBase.readinto1"><code class="docutils literal notranslate">readinto1()</code></a></li> <li><a class="reference internal" href="#io.BufferedIOBase.write"><code class="docutils literal notranslate">write()</code></a></li> </ul> </li> </ul> </li> <li><a class="reference internal" href="#raw-file-i-o">Raw File I/O</a><ul> <li><a class="reference internal" href="#io.FileIO"><code class="docutils literal notranslate">FileIO</code></a><ul> <li><a class="reference internal" href="#io.FileIO.mode"><code class="docutils literal notranslate">mode</code></a></li> <li><a class="reference internal" href="#io.FileIO.name"><code class="docutils literal notranslate">name</code></a></li> </ul> </li> </ul> </li> <li><a class="reference internal" href="#buffered-streams">Buffered Streams</a><ul> <li><a class="reference internal" href="#io.BytesIO"><code class="docutils literal notranslate">BytesIO</code></a><ul> <li><a class="reference internal" href="#io.BytesIO.getbuffer"><code class="docutils literal notranslate">getbuffer()</code></a></li> <li><a class="reference internal" href="#io.BytesIO.getvalue"><code class="docutils literal notranslate">getvalue()</code></a></li> <li><a class="reference internal" href="#io.BytesIO.read1"><code class="docutils literal notranslate">read1()</code></a></li> <li><a class="reference internal" href="#io.BytesIO.readinto1"><code class="docutils literal notranslate">readinto1()</code></a></li> </ul> </li> <li><a class="reference internal" href="#io.BufferedReader"><code class="docutils literal notranslate">BufferedReader</code></a><ul> <li><a class="reference internal" href="#io.BufferedReader.peek"><code class="docutils literal notranslate">peek()</code></a></li> <li><a class="reference internal" href="#io.BufferedReader.read"><code class="docutils literal notranslate">read()</code></a></li> <li><a class="reference internal" href="#io.BufferedReader.read1"><code class="docutils literal notranslate">read1()</code></a></li> </ul> </li> <li><a class="reference internal" href="#io.BufferedWriter"><code class="docutils literal notranslate">BufferedWriter</code></a><ul> <li><a class="reference internal" href="#io.BufferedWriter.flush"><code class="docutils literal notranslate">flush()</code></a></li> <li><a class="reference internal" href="#io.BufferedWriter.write"><code class="docutils literal notranslate">write()</code></a></li> </ul> </li> <li><a class="reference internal" href="#io.BufferedRandom"><code class="docutils literal notranslate">BufferedRandom</code></a></li> <li><a class="reference internal" href="#io.BufferedRWPair"><code class="docutils literal notranslate">BufferedRWPair</code></a></li> </ul> </li> <li><a class="reference internal" href="#id1">Text I/O</a><ul> <li><a class="reference internal" href="#io.TextIOBase"><code class="docutils literal notranslate">TextIOBase</code></a><ul> <li><a class="reference internal" href="#io.TextIOBase.encoding"><code class="docutils literal notranslate">encoding</code></a></li> <li><a class="reference internal" href="#io.TextIOBase.errors"><code class="docutils literal notranslate">errors</code></a></li> <li><a class="reference internal" href="#io.TextIOBase.newlines"><code class="docutils literal notranslate">newlines</code></a></li> <li><a class="reference internal" href="#io.TextIOBase.buffer"><code class="docutils literal notranslate">buffer</code></a></li> <li><a class="reference internal" href="#io.TextIOBase.detach"><code class="docutils literal notranslate">detach()</code></a></li> <li><a class="reference internal" href="#io.TextIOBase.read"><code class="docutils literal notranslate">read()</code></a></li> <li><a class="reference internal" href="#io.TextIOBase.readline"><code class="docutils literal notranslate">readline()</code></a></li> <li><a class="reference internal" href="#io.TextIOBase.seek"><code class="docutils literal notranslate">seek()</code></a></li> <li><a class="reference internal" href="#io.TextIOBase.tell"><code class="docutils literal notranslate">tell()</code></a></li> <li><a class="reference internal" href="#io.TextIOBase.write"><code class="docutils literal notranslate">write()</code></a></li> </ul> </li> <li><a class="reference internal" href="#io.TextIOWrapper"><code class="docutils literal notranslate">TextIOWrapper</code></a><ul> <li><a class="reference internal" href="#io.TextIOWrapper.line_buffering"><code class="docutils literal notranslate">line_buffering</code></a></li> <li><a class="reference internal" href="#io.TextIOWrapper.write_through"><code class="docutils literal notranslate">write_through</code></a></li> <li><a class="reference internal" href="#io.TextIOWrapper.reconfigure"><code class="docutils literal notranslate">reconfigure()</code></a></li> <li><a class="reference internal" href="#io.TextIOWrapper.seek"><code class="docutils literal notranslate">seek()</code></a></li> <li><a class="reference internal" href="#io.TextIOWrapper.tell"><code class="docutils literal notranslate">tell()</code></a></li> </ul> </li> <li><a class="reference internal" href="#io.StringIO"><code class="docutils literal notranslate">StringIO</code></a><ul> <li><a class="reference internal" href="#io.StringIO.getvalue"><code class="docutils literal notranslate">getvalue()</code></a></li> </ul> </li> <li><a class="reference internal" href="#io.IncrementalNewlineDecoder"><code class="docutils literal notranslate">IncrementalNewlineDecoder</code></a></li> </ul> </li> </ul> </li> <li><a class="reference internal" href="#performance">Performance</a><ul> <li><a class="reference internal" href="#id2">Binary I/O</a></li> <li><a class="reference internal" href="#id3">Text I/O</a></li> <li><a class="reference internal" href="#multi-threading">Multi-threading</a></li> <li><a class="reference internal" href="#reentrancy">Reentrancy</a></li> </ul> </li> </ul> </li> </ul> </div> <div> <h4>Previous topic</h4> <a href="os.html" title="previous chapter"><code class="xref py py-mod docutils literal notranslate">os</code> — Miscellaneous operating system interfaces</a> </div> <div> <h4>Next topic</h4> <a href="time.html" 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