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<!DOCTYPE html> <html lang="en"> <head> <meta charset="utf-8"> <meta name="viewport" content="width=device-width, initial-scale=1.0"> <meta name="color-scheme" content="light dark"> <title>PEP 390 – Static metadata for Distutils | peps.python.org</title> <link rel="shortcut icon" href="../_static/py.png"> <link rel="canonical" href="https://peps.python.org/pep-0390/"> <link rel="stylesheet" href="../_static/style.css" type="text/css"> <link rel="stylesheet" href="../_static/mq.css" type="text/css"> <link rel="stylesheet" href="../_static/pygments.css" type="text/css" media="(prefers-color-scheme: light)" id="pyg-light"> <link rel="stylesheet" href="../_static/pygments_dark.css" type="text/css" media="(prefers-color-scheme: dark)" id="pyg-dark"> <link rel="alternate" type="application/rss+xml" title="Latest PEPs" href="https://peps.python.org/peps.rss"> <meta property="og:title" content='PEP 390 – Static metadata for Distutils | peps.python.org'> <meta property="og:description" 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class="colour-scheme-icon-when-auto"><use href="#svg-sun-half"></use></svg> <svg aria-hidden="true" class="colour-scheme-icon-when-dark"><use href="#svg-moon"></use></svg> <svg aria-hidden="true" class="colour-scheme-icon-when-light"><use href="#svg-sun"></use></svg> Toggle light / dark / auto colour theme </button> </header> <article> <section id="pep-content"> <h1 class="page-title">PEP 390 – Static metadata for Distutils</h1> <dl class="rfc2822 field-list simple"> <dt class="field-odd">Author:</dt> <dd class="field-odd">Tarek Ziadé <tarek at ziade.org></dd> <dt class="field-even">BDFL-Delegate:</dt> <dd class="field-even">Alyssa Coghlan</dd> <dt class="field-odd">Discussions-To:</dt> <dd class="field-odd"><a class="reference external" href="https://mail.python.org/archives/list/distutils-sig@python.org/">Distutils-SIG list</a></dd> <dt class="field-even">Status:</dt> <dd class="field-even"><abbr title="Formally declined and will not be accepted">Rejected</abbr></dd> <dt class="field-odd">Type:</dt> <dd class="field-odd"><abbr title="Normative PEP with a new feature for Python, implementation change for CPython or interoperability standard for the ecosystem">Standards Track</abbr></dd> <dt class="field-even">Topic:</dt> <dd class="field-even"><a class="reference external" href="../topic/packaging/">Packaging</a></dd> <dt class="field-odd">Created:</dt> <dd class="field-odd">10-Oct-2009</dd> <dt class="field-even">Python-Version:</dt> <dd class="field-even">2.7, 3.2</dd> <dt class="field-odd">Post-History:</dt> <dd class="field-odd"></dd> <dt class="field-even">Resolution:</dt> <dd class="field-even"><a class="reference external" href="https://mail.python.org/pipermail/distutils-sig/2013-April/020597.html">Distutils-SIG message</a></dd> </dl> <hr class="docutils" /> <section id="contents"> <details><summary>Table of Contents</summary><ul class="simple"> <li><a class="reference internal" href="#abstract">Abstract</a></li> <li><a class="reference internal" href="#rejection-notice">Rejection Notice</a></li> <li><a class="reference internal" href="#rationale">Rationale</a></li> <li><a class="reference internal" href="#adding-a-metadata-section-in-setup-cfg">Adding a <code class="docutils literal notranslate">metadata</code> section in <code class="docutils literal notranslate">setup.cfg</code></a></li> <li><a class="reference internal" href="#multi-lines-values">Multi-lines values</a></li> <li><a class="reference internal" href="#context-dependant-sections">Context-dependant sections</a></li> <li><a class="reference internal" href="#impact-on-pkg-info-generation-and-pep-314">Impact on PKG-INFO generation and PEP 314</a></li> <li><a class="reference internal" href="#compatibility">Compatibility</a></li> <li><a class="reference internal" href="#limitations">Limitations</a></li> <li><a class="reference internal" href="#acknowledgments">Acknowledgments</a></li> <li><a class="reference internal" href="#copyright">Copyright</a></li> </ul> </details></section> <section id="abstract"> <h2><a class="toc-backref" href="#abstract" role="doc-backlink">Abstract</a></h2> This PEP describes a new section and a new format for the <code class="docutils literal notranslate">setup.cfg</code> file, that allows describing the Metadata of a package without using <code class="docutils literal notranslate">setup.py</code>. </section> <section id="rejection-notice"> <h2><a class="toc-backref" href="#rejection-notice" role="doc-backlink">Rejection Notice</a></h2> As distutils2 is no longer going to be incorporated into the standard library, this PEP was rejected by Alyssa Coghlan in late April, 2013. A replacement PEP based on <a class="pep reference internal" href="../pep-0426/" title="PEP 426 – Metadata for Python Software Packages 2.0">PEP 426</a> (metadata 2.0) will be created that defines the minimum amount of information needed to generate an sdist archive given a source tarball or VCS checkout. </section> <section id="rationale"> <h2><a class="toc-backref" href="#rationale" role="doc-backlink">Rationale</a></h2> Today, if you want to list all the Metadata of a distribution (see <a class="pep reference internal" href="../pep-0314/" title="PEP 314 – Metadata for Python Software Packages 1.1">PEP 314</a>) that is not installed, you need to use the <code class="docutils literal notranslate">setup.py</code> command line interface. So, basically, you download it, and run: <div class="highlight-default notranslate"><div class="highlight"><pre>$ python setup.py --name Distribute $ python setup.py --version 0.6.4 </pre></div> </div> Where <code class="docutils literal notranslate">name</code> and <code class="docutils literal notranslate">version</code> are metadata fields. This is working fine but as soon as the developers add more code in <code class="docutils literal notranslate">setup.py</code>, this feature might break or in worst cases might do unwanted things on the target system. Moreover, when an OS packager wants to get the metadata of a distribution he is re-packaging, he might encounter some problems to understand the <code class="docutils literal notranslate">setup.py</code> file he’s working with. So the rationale of this PEP is to provide a way to declare the metadata in a static configuration file alongside <code class="docutils literal notranslate">setup.py</code> that doesn’t require any third party code to run. </section> <section id="adding-a-metadata-section-in-setup-cfg"> <h2><a class="toc-backref" href="#adding-a-metadata-section-in-setup-cfg" role="doc-backlink">Adding a <code class="docutils literal notranslate">metadata</code> section in <code class="docutils literal notranslate">setup.cfg</code></a></h2> The first thing we want to introduce is a <code class="docutils literal notranslate">[metadata]</code> section, in the <code class="docutils literal notranslate">setup.cfg</code> file, that may contain any field from the Metadata: <div class="highlight-default notranslate"><div class="highlight"><pre>[metadata] name = Distribute version = 0.6.4 </pre></div> </div> The <code class="docutils literal notranslate">setup.cfg</code> file is used to avoid adding yet another configuration file to work with in Distutils. This file is already read by Distutils when a command is executed, and if the <code class="docutils literal notranslate">metadata</code> section is found, it will be used to fill the metadata fields. If an option that corresponds to a Metadata field is given to <code class="docutils literal notranslate">setup()</code>, it will override the value that was possibly present in <code class="docutils literal notranslate">setup.cfg</code>. Notice that <code class="docutils literal notranslate">setup.py</code> is still used and can be required to define some options that are not part of the Metadata fields. For instance, the <code class="docutils literal notranslate">sdist</code> command can use options like <code class="docutils literal notranslate">packages</code> or <code class="docutils literal notranslate">scripts</code>. </section> <section id="multi-lines-values"> <h2><a class="toc-backref" href="#multi-lines-values" role="doc-backlink">Multi-lines values</a></h2> Some Metadata fields can have multiple values. To keep <code class="docutils literal notranslate">setup.cfg</code> compatible with <code class="docutils literal notranslate">ConfigParser</code> and the <a class="rfc reference external" href="https://datatracker.ietf.org/doc/html/rfc822.html">RFC 822</a> <code class="docutils literal notranslate">LONG HEADER FIELDS</code> (see section 3.1.1), these are expressed with <code class="docutils literal notranslate">,</code>-separated values: <div class="highlight-default notranslate"><div class="highlight"><pre>requires = pywin32, bar > 1.0, foo </pre></div> </div> When this variable is read, the values are parsed and transformed into a list: <code class="docutils literal notranslate">['pywin32', 'bar > 1.0', 'foo']</code>. </section> <section id="context-dependant-sections"> <h2><a class="toc-backref" href="#context-dependant-sections" role="doc-backlink">Context-dependant sections</a></h2> The <code class="docutils literal notranslate">metadata</code> section will also be able to use context-dependant sections. A context-dependant section is a section with a condition about the execution environment. Here’s some examples: <div class="highlight-default notranslate"><div class="highlight"><pre>[metadata] name = Distribute version = 0.6.4 [metadata:sys_platform == 'win32'] requires = pywin32, bar > 1.0 obsoletes = pywin31 [metadata:os_machine == 'i386'] requires = foo [metadata:python_version == '2.4' or python_version == '2.5'] requires = bar [metadata:'linux' in sys_platform] requires = baz </pre></div> </div> Every <code class="docutils literal notranslate">[metadata:condition]</code> section will be used only if the condition is met when the file is read. The background motivation for these context-dependant sections is to be able to define requirements that varies depending on the platform the distribution might be installed on. (see <a class="pep reference internal" href="../pep-0314/" title="PEP 314 – Metadata for Python Software Packages 1.1">PEP 314</a>). The micro-language behind this is the simplest possible: it compares only strings, with the <code class="docutils literal notranslate">==</code> and <code class="docutils literal notranslate">in</code> operators (and their opposites), and with the ability to combine expressions. It makes it also easy to understand to non-pythoneers. The pseudo-grammar is <div class="highlight-default notranslate"><div class="highlight"><pre>EXPR [in|==|!=|not in] EXPR [or|and] ... </pre></div> </div> where <code class="docutils literal notranslate">EXPR</code> belongs to any of those: <ul class="simple"> <li>python_version = ‘%s.%s’ % (sys.version_info[0], sys.version_info[1])</li> <li>os_name = os.name</li> <li>sys_platform = sys.platform</li> <li>platform_version = platform.version()</li> <li>platform_machine = platform.machine()</li> <li>a free string, like <code class="docutils literal notranslate">2.4</code>, or <code class="docutils literal notranslate">win32</code></li> </ul> Notice that <code class="docutils literal notranslate">in</code> is restricted to strings, meaning that it is not possible to use other sequences like tuples or lists on the right side. Distutils will provide a function that is able to generate the metadata of a distribution, given a <code class="docutils literal notranslate">setup.cfg</code> file, for the execution environment: <div class="highlight-default notranslate"><div class="highlight"><pre>>>> from distutils.util import local_metadata >>> local_metadata('setup.cfg') <DistributionMetadata instance> </pre></div> </div> This means that a vanilla Python will be able to read the metadata of a package without running any third party code. Notice that this feature is not restricted to the <code class="docutils literal notranslate">metadata</code> namespace. Consequently, any other section can be extended with such context-dependant sections. </section> <section id="impact-on-pkg-info-generation-and-pep-314"> <h2><a class="toc-backref" href="#impact-on-pkg-info-generation-and-pep-314" role="doc-backlink">Impact on PKG-INFO generation and PEP 314</a></h2> When <code class="docutils literal notranslate">PKG-INFO</code> is generated by Distutils, every field that relies on a condition will have that condition written at the end of the line, after a <code class="docutils literal notranslate">;</code> separator: <div class="highlight-default notranslate"><div class="highlight"><pre>Metadata-Version: 1.2 Name: distribute Version: 0.6.4 ... Requires: pywin32, bar > 1.0; sys_platform == 'win32' Requires: foo; os_machine == 'i386' Requires: bar; python_version == '2.4' or python_version == '2.5' Requires: baz; 'linux' in sys_platform Obsoletes = pywin31; sys_platform == 'win32' ... Classifier: Development Status :: 5 - Production/Stable Classifier: Intended Audience :: Developers Classifier: License :: OSI Approved :: Python Software Foundation License </pre></div> </div> Notice that this file can be opened with the <code class="docutils literal notranslate">DistributionMetadata</code> class. This class will be able to use the micro-language using the execution environment. Let’s run in on a <code class="docutils literal notranslate">Python 2.5 i386 Linux</code>: <div class="highlight-default notranslate"><div class="highlight"><pre>>>> from distutils.dist import DistributionMetadata >>> metadata = DistributionMetadata('PKG_INFO') >>> metadata.get_requires() ['foo', 'bar', 'baz'] </pre></div> </div> The execution environment can be overridden in case we want to get the metadata for another environment: <div class="highlight-default notranslate"><div class="highlight"><pre>>>> env = {'python_version': '2.4', ... 'os_name': 'nt', ... 'sys_platform': 'win32', ... 'platform_version': 'MVCC++ 6.0' ... 'platform_machine': 'i386'} ... >>> metadata = DistributionMetadata('PKG_INFO', environment=env) >>> metadata.get_requires() ['bar > 1.0', 'foo', 'bar'] </pre></div> </div> <a class="pep reference internal" href="../pep-0314/" title="PEP 314 – Metadata for Python Software Packages 1.1">PEP 314</a> is changed accordingly, meaning that each field will be able to have that extra condition marker. </section> <section id="compatibility"> <h2><a class="toc-backref" href="#compatibility" role="doc-backlink">Compatibility</a></h2> This change is based on a new metadata <code class="docutils literal notranslate">1.2</code> format meaning that Distutils will be able to distinguish old PKG-INFO files from new ones. The <code class="docutils literal notranslate">setup.cfg</code> file change will stay <code class="docutils literal notranslate">ConfigParser</code>-compatible and will not break existing <code class="docutils literal notranslate">setup.cfg</code> files. </section> <section id="limitations"> <h2><a class="toc-backref" href="#limitations" role="doc-backlink">Limitations</a></h2> We are not providing <code class="docutils literal notranslate"><</code> and <code class="docutils literal notranslate">></code> operators at this time, and <code class="docutils literal notranslate">python_version</code> is a regular string. This implies using <code class="docutils literal notranslate">or</code> operators when a section needs to be restricted to a couple of Python versions. Although, if <a class="pep reference internal" href="../pep-0386/" title="PEP 386 – Changing the version comparison module in Distutils">PEP 386</a> is accepted, <code class="docutils literal notranslate">python_version</code> could be changed internally into something comparable with strings, and <code class="docutils literal notranslate"><</code> and <code class="docutils literal notranslate">></code> operators introduced. Last, if a distribution is unable to set all metadata fields in <code class="docutils literal notranslate">setup.cfg</code>, that’s fine, the fields will be set to <code class="docutils literal notranslate">UNKNOWN</code> when <code class="docutils literal notranslate">local_metadata</code> is called. Getting <code class="docutils literal notranslate">UNKNOWN</code> values will mean that it might be necessary to run the <code class="docutils literal notranslate">setup.py</code> command line interface to get the whole set of metadata. </section> <section id="acknowledgments"> <h2><a class="toc-backref" href="#acknowledgments" role="doc-backlink">Acknowledgments</a></h2> The Distutils-SIG. </section> <section id="copyright"> <h2><a class="toc-backref" href="#copyright" role="doc-backlink">Copyright</a></h2> This document has been placed in the public domain. </section> </section> <hr class="docutils" /> Source: <a class="reference external" href="https://github.com/python/peps/blob/main/peps/pep-0390.rst">https://github.com/python/peps/blob/main/peps/pep-0390.rst</a> Last modified: <a class="reference external" href="https://github.com/python/peps/commits/main/peps/pep-0390.rst">2025-02-01 08:59:27 GMT</a> </article> <nav id="pep-sidebar"> <h2>Contents</h2> <ul> <li><a class="reference internal" href="#abstract">Abstract</a></li> <li><a class="reference internal" href="#rejection-notice">Rejection Notice</a></li> <li><a class="reference internal" href="#rationale">Rationale</a></li> <li><a class="reference internal" href="#adding-a-metadata-section-in-setup-cfg">Adding a <code class="docutils literal notranslate">metadata</code> section in <code class="docutils literal notranslate">setup.cfg</code></a></li> <li><a class="reference internal" href="#multi-lines-values">Multi-lines values</a></li> <li><a class="reference internal" href="#context-dependant-sections">Context-dependant sections</a></li> <li><a class="reference internal" href="#impact-on-pkg-info-generation-and-pep-314">Impact on PKG-INFO generation and PEP 314</a></li> <li><a class="reference internal" href="#compatibility">Compatibility</a></li> <li><a class="reference internal" href="#limitations">Limitations</a></li> <li><a class="reference internal" href="#acknowledgments">Acknowledgments</a></li> <li><a class="reference internal" href="#copyright">Copyright</a></li> </ul> <a id="source" href="https://github.com/python/peps/blob/main/peps/pep-0390.rst">Page Source (GitHub)</a> </nav> </section> <script src="../_static/colour_scheme.js"></script> <script src="../_static/wrap_tables.js"></script> <script src="../_static/sticky_banner.js"></script> </body> </html>