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<h1>Python Enhancement Proposals</h1>
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<h1 class="page-title">PEP 365 – Adding the pkg_resources module</h1>
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<dl class="rfc2822 field-list simple">
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<dt class="field-odd">Author<span class="colon">:</span></dt>
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<dd class="field-odd">Phillip J. Eby <pje at telecommunity.com></dd>
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<dt class="field-even">Status<span class="colon">:</span></dt>
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<dd class="field-even"><abbr title="Formally declined and will not be accepted">Rejected</abbr></dd>
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<dt class="field-odd">Type<span class="colon">:</span></dt>
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<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>
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<dt class="field-even">Topic<span class="colon">:</span></dt>
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<dd class="field-even"><a class="reference external" href="../topic/packaging/">Packaging</a></dd>
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<dt class="field-odd">Created<span class="colon">:</span></dt>
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<dd class="field-odd">30-Apr-2007</dd>
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<dt class="field-even">Post-History<span class="colon">:</span></dt>
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<dd class="field-even">30-Apr-2007</dd>
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<details><summary>Table of Contents</summary><ul class="simple">
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<li><a class="reference internal" href="#abstract">Abstract</a></li>
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<li><a class="reference internal" href="#proposal">Proposal</a></li>
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<li><a class="reference internal" href="#rationale">Rationale</a></li>
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<li><a class="reference internal" href="#implementation-and-documentation">Implementation and Documentation</a></li>
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<li><a class="reference internal" href="#copyright">Copyright</a></li>
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</ul>
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</details></section>
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<section id="abstract">
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<h2><a class="toc-backref" href="#abstract" role="doc-backlink">Abstract</a></h2>
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<p>This PEP proposes adding an enhanced version of the <code class="docutils literal notranslate"><span class="pre">pkg_resources</span></code>
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module to the standard library.</p>
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<p><code class="docutils literal notranslate"><span class="pre">pkg_resources</span></code> is a module used to find and manage Python
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package/version dependencies and access bundled files and resources,
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including those inside of zipped <code class="docutils literal notranslate"><span class="pre">.egg</span></code> files. Currently,
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<code class="docutils literal notranslate"><span class="pre">pkg_resources</span></code> is only available through installing the entire
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<code class="docutils literal notranslate"><span class="pre">setuptools</span></code> distribution, but it does not depend on any other part
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of setuptools; in effect, it comprises the entire runtime support
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library for Python Eggs, and is independently useful.</p>
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<p>In addition, with one feature addition, this module could support
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easy bootstrap installation of several Python package management
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tools, including <code class="docutils literal notranslate"><span class="pre">setuptools</span></code>, <code class="docutils literal notranslate"><span class="pre">workingenv</span></code>, and <code class="docutils literal notranslate"><span class="pre">zc.buildout</span></code>.</p>
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</section>
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<section id="proposal">
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<h2><a class="toc-backref" href="#proposal" role="doc-backlink">Proposal</a></h2>
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<p>Rather than proposing to include <code class="docutils literal notranslate"><span class="pre">setuptools</span></code> in the standard
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library, this PEP proposes only that <code class="docutils literal notranslate"><span class="pre">pkg_resources</span></code> be added to the
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standard library for Python 2.6 and 3.0. <code class="docutils literal notranslate"><span class="pre">pkg_resources</span></code> is
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considerably more stable than the rest of setuptools, with virtually
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no new features being added in the last 12 months.</p>
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<p>However, this PEP also proposes that a new feature be added to
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<code class="docutils literal notranslate"><span class="pre">pkg_resources</span></code>, before being added to the stdlib. Specifically, it
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should be possible to do something like:</p>
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<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">python</span> <span class="o">-</span><span class="n">m</span> <span class="n">pkg_resources</span> <span class="n">SomePackage</span><span class="o">==</span><span class="mf">1.2</span>
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</pre></div>
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</div>
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<p>to request downloading and installation of <code class="docutils literal notranslate"><span class="pre">SomePackage</span></code> from PyPI.
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This feature would <em>not</em> be a replacement for <code class="docutils literal notranslate"><span class="pre">easy_install</span></code>;
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instead, it would rely on <code class="docutils literal notranslate"><span class="pre">SomePackage</span></code> having pure-Python <code class="docutils literal notranslate"><span class="pre">.egg</span></code>
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files listed for download via the PyPI XML-RPC API, and the eggs would
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be placed in the <code class="docutils literal notranslate"><span class="pre">$PYTHON_EGG_CACHE</span></code> directory, where they would
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<strong>not</strong> be importable by default. (And no scripts would be installed.)
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However, if the download egg contains installation bootstrap code, it
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will be given a chance to run.</p>
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<p>These restrictions would allow the code to be extremely simple, yet
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still powerful enough to support users downloading package management
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tools such as <code class="docutils literal notranslate"><span class="pre">setuptools</span></code>, <code class="docutils literal notranslate"><span class="pre">workingenv</span></code> and <code class="docutils literal notranslate"><span class="pre">zc.buildout</span></code>,
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simply by supplying the tool’s name on the command line.</p>
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</section>
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<section id="rationale">
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<h2><a class="toc-backref" href="#rationale" role="doc-backlink">Rationale</a></h2>
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<p>Many users have requested that <code class="docutils literal notranslate"><span class="pre">setuptools</span></code> be included in the
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standard library, to save users needing to go through the awkward
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process of bootstrapping it. However, most of the bootstrapping
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complexity comes from the fact that setuptools-installed code cannot
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use the <code class="docutils literal notranslate"><span class="pre">pkg_resources</span></code> runtime module unless setuptools is already
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installed. Thus, installing setuptools requires (in a sense) that
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setuptools already be installed.</p>
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<p>Other Python package management tools, such as <code class="docutils literal notranslate"><span class="pre">workingenv</span></code> and
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<code class="docutils literal notranslate"><span class="pre">zc.buildout</span></code>, have similar bootstrapping issues, since they both
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make use of setuptools, but also want to provide users with something
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approaching a “one-step install”. The complexity of creating bootstrap
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utilities for these and any other such tools that arise in future, is
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greatly reduced if <code class="docutils literal notranslate"><span class="pre">pkg_resources</span></code> is already present, and is also
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able to download pre-packaged eggs from PyPI.</p>
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<p>(It would also mean that setuptools would not need to be installed
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in order to simply <em>use</em> eggs, as opposed to building them.)</p>
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<p>Finally, in addition to providing access to eggs built via setuptools
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or other packaging tools, it should be noted that since Python 2.5,
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the distutils install package metadata (aka <code class="docutils literal notranslate"><span class="pre">PKG-INFO</span></code>) files that
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can be read by <code class="docutils literal notranslate"><span class="pre">pkg_resources</span></code> to identify what distributions are
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already on <code class="docutils literal notranslate"><span class="pre">sys.path</span></code>. In environments where Python packages are
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installed using system package tools (like RPM), the <code class="docutils literal notranslate"><span class="pre">pkg_resources</span></code>
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module provides an API for detecting what versions of what packages
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are installed, even if those packages were installed via the distutils
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instead of setuptools.</p>
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</section>
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<section id="implementation-and-documentation">
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<h2><a class="toc-backref" href="#implementation-and-documentation" role="doc-backlink">Implementation and Documentation</a></h2>
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<p>The <code class="docutils literal notranslate"><span class="pre">pkg_resources</span></code> implementation is maintained in the Python
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SVN repository under <code class="docutils literal notranslate"><span class="pre">/sandbox/trunk/setuptools/</span></code>; see
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<code class="docutils literal notranslate"><span class="pre">pkg_resources.py</span></code> and <code class="docutils literal notranslate"><span class="pre">pkg_resources.txt</span></code>. Documentation for the
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egg format(s) supported by <code class="docutils literal notranslate"><span class="pre">pkg_resources</span></code> can be found in
|
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<code class="docutils literal notranslate"><span class="pre">doc/formats.txt</span></code>. HTML versions of these documents are available
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at:</p>
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<ul class="simple">
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<li><a class="reference external" href="http://peak.telecommunity.com/DevCenter/PkgResources">http://peak.telecommunity.com/DevCenter/PkgResources</a> and</li>
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<li><a class="reference external" href="http://peak.telecommunity.com/DevCenter/EggFormats">http://peak.telecommunity.com/DevCenter/EggFormats</a></li>
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</ul>
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<p>(These HTML versions are for setuptools 0.6; they may not reflect all
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of the changes found in the Subversion trunk’s <code class="docutils literal notranslate"><span class="pre">.txt</span></code> versions.)</p>
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</section>
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<section id="copyright">
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<h2><a class="toc-backref" href="#copyright" role="doc-backlink">Copyright</a></h2>
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<p>This document has been placed in the public domain.</p>
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</section>
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</section>
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<hr class="docutils" />
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<p>Source: <a class="reference external" href="https://github.com/python/peps/blob/main/peps/pep-0365.rst">https://github.com/python/peps/blob/main/peps/pep-0365.rst</a></p>
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<p>Last modified: <a class="reference external" href="https://github.com/python/peps/commits/main/peps/pep-0365.rst">2023-09-09 17:39:29 GMT</a></p>
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<h2>Contents</h2>
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<ul>
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<li><a class="reference internal" href="#abstract">Abstract</a></li>
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<li><a class="reference internal" href="#proposal">Proposal</a></li>
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<li><a class="reference internal" href="#rationale">Rationale</a></li>
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<li><a class="reference internal" href="#implementation-and-documentation">Implementation and Documentation</a></li>
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<li><a class="reference internal" href="#copyright">Copyright</a></li>
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</ul>
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<br>
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