CINXE.COM

<!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 365 – Adding the pkg_resources module | peps.python.org</title> <link rel="shortcut icon" href="../_static/py.png"> <link rel="canonical" href="https://peps.python.org/pep-0365/"> <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 365 – Adding the pkg_resources module | peps.python.org'> <meta property="og:description" content="This PEP proposes adding an enhanced version of the pkg_resources module to the standard library."> <meta property="og:type" content="website"> <meta property="og:url" content="https://peps.python.org/pep-0365/"> <meta property="og:site_name" content="Python Enhancement Proposals (PEPs)"> <meta property="og:image" content="https://peps.python.org/_static/og-image.png"> <meta property="og:image:alt" content="Python PEPs"> <meta property="og:image:width" content="200"> <meta property="og:image:height" content="200"> <meta name="description" content="This PEP proposes adding an enhanced version of the pkg_resources module to the standard library."> <meta name="theme-color" content="#3776ab"> </head> <body> <svg xmlns="http://www.w3.org/2000/svg" style="display: none;"> <symbol id="svg-sun-half" viewBox="0 0 24 24" pointer-events="all"> <title>Following system colour scheme</title> <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round"> <circle cx="12" cy="12" r="9"></circle> <path d="M12 3v18m0-12l4.65-4.65M12 14.3l7.37-7.37M12 19.6l8.85-8.85"></path> </svg> </symbol> <symbol id="svg-moon" viewBox="0 0 24 24" pointer-events="all"> <title>Selected dark colour scheme</title> <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round"> <path stroke="none" d="M0 0h24v24H0z" fill="none"></path> <path d="M12 3c.132 0 .263 0 .393 0a7.5 7.5 0 0 0 7.92 12.446a9 9 0 1 1 -8.313 -12.454z"></path> </svg> </symbol> <symbol id="svg-sun" viewBox="0 0 24 24" pointer-events="all"> <title>Selected light colour scheme</title> <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round"> <circle cx="12" cy="12" r="5"></circle> <line x1="12" y1="1" x2="12" y2="3"></line> <line x1="12" y1="21" x2="12" y2="23"></line> <line x1="4.22" y1="4.22" x2="5.64" y2="5.64"></line> <line x1="18.36" y1="18.36" x2="19.78" y2="19.78"></line> <line x1="1" y1="12" x2="3" y2="12"></line> <line x1="21" y1="12" x2="23" y2="12"></line> <line x1="4.22" y1="19.78" x2="5.64" y2="18.36"></line> <line x1="18.36" y1="5.64" x2="19.78" y2="4.22"></line> </svg> </symbol> </svg> <script> document.documentElement.dataset.colour_scheme = localStorage.getItem("colour_scheme") || "auto" </script> <section id="pep-page-section"> <header> <h1>Python Enhancement Proposals</h1> <ul class="breadcrumbs"> <li><a href="https://www.python.org/" title="The Python Programming Language">Python</a> » </li> <li><a href="../pep-0000/">PEP Index</a> » </li> <li>PEP 365</li> </ul> <button id="colour-scheme-cycler" onClick="setColourScheme(nextColourScheme())"> <svg aria-hidden="true" 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> <span class="visually-hidden">Toggle light / dark / auto colour theme</span> </button> </header> <article> <section id="pep-content"> <h1 class="page-title">PEP 365 – Adding the pkg_resources module</h1> <dl class="rfc2822 field-list simple"> <dt class="field-odd">Author<span class="colon">:</span></dt> <dd class="field-odd">Phillip J. Eby <pje at telecommunity.com></dd> <dt class="field-even">Status<span class="colon">:</span></dt> <dd class="field-even"><abbr title="Formally declined and will not be accepted">Rejected</abbr></dd> <dt class="field-odd">Type<span class="colon">:</span></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<span class="colon">:</span></dt> <dd class="field-even"><a class="reference external" href="../topic/packaging/">Packaging</a></dd> <dt class="field-odd">Created<span class="colon">:</span></dt> <dd class="field-odd">30-Apr-2007</dd> <dt class="field-even">Post-History<span class="colon">:</span></dt> <dd class="field-even">30-Apr-2007</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="#proposal">Proposal</a></li> <li><a class="reference internal" href="#rationale">Rationale</a></li> <li><a class="reference internal" href="#implementation-and-documentation">Implementation and Documentation</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> <p>This PEP proposes adding an enhanced version of the <code class="docutils literal notranslate"><span class="pre">pkg_resources</span></code> module to the standard library.</p> <p><code class="docutils literal notranslate"><span class="pre">pkg_resources</span></code> is a module used to find and manage Python package/version dependencies and access bundled files and resources, including those inside of zipped <code class="docutils literal notranslate"><span class="pre">.egg</span></code> files. Currently, <code class="docutils literal notranslate"><span class="pre">pkg_resources</span></code> is only available through installing the entire <code class="docutils literal notranslate"><span class="pre">setuptools</span></code> distribution, but it does not depend on any other part of setuptools; in effect, it comprises the entire runtime support library for Python Eggs, and is independently useful.</p> <p>In addition, with one feature addition, this module could support easy bootstrap installation of several Python package management 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> </section> <section id="proposal"> <h2><a class="toc-backref" href="#proposal" role="doc-backlink">Proposal</a></h2> <p>Rather than proposing to include <code class="docutils literal notranslate"><span class="pre">setuptools</span></code> in the standard library, this PEP proposes only that <code class="docutils literal notranslate"><span class="pre">pkg_resources</span></code> be added to the standard library for Python 2.6 and 3.0. <code class="docutils literal notranslate"><span class="pre">pkg_resources</span></code> is considerably more stable than the rest of setuptools, with virtually no new features being added in the last 12 months.</p> <p>However, this PEP also proposes that a new feature be added to <code class="docutils literal notranslate"><span class="pre">pkg_resources</span></code>, before being added to the stdlib. Specifically, it should be possible to do something like:</p> <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> </pre></div> </div> <p>to request downloading and installation of <code class="docutils literal notranslate"><span class="pre">SomePackage</span></code> from PyPI. This feature would <em>not</em> be a replacement for <code class="docutils literal notranslate"><span class="pre">easy_install</span></code>; 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> files listed for download via the PyPI XML-RPC API, and the eggs would be placed in the <code class="docutils literal notranslate"><span class="pre">$PYTHON_EGG_CACHE</span></code> directory, where they would <strong>not</strong> be importable by default. (And no scripts would be installed.) However, if the download egg contains installation bootstrap code, it will be given a chance to run.</p> <p>These restrictions would allow the code to be extremely simple, yet still powerful enough to support users downloading package management 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>, simply by supplying the tool’s name on the command line.</p> </section> <section id="rationale"> <h2><a class="toc-backref" href="#rationale" role="doc-backlink">Rationale</a></h2> <p>Many users have requested that <code class="docutils literal notranslate"><span class="pre">setuptools</span></code> be included in the standard library, to save users needing to go through the awkward process of bootstrapping it. However, most of the bootstrapping complexity comes from the fact that setuptools-installed code cannot use the <code class="docutils literal notranslate"><span class="pre">pkg_resources</span></code> runtime module unless setuptools is already installed. Thus, installing setuptools requires (in a sense) that setuptools already be installed.</p> <p>Other Python package management tools, such as <code class="docutils literal notranslate"><span class="pre">workingenv</span></code> and <code class="docutils literal notranslate"><span class="pre">zc.buildout</span></code>, have similar bootstrapping issues, since they both make use of setuptools, but also want to provide users with something approaching a “one-step install”. The complexity of creating bootstrap utilities for these and any other such tools that arise in future, is greatly reduced if <code class="docutils literal notranslate"><span class="pre">pkg_resources</span></code> is already present, and is also able to download pre-packaged eggs from PyPI.</p> <p>(It would also mean that setuptools would not need to be installed in order to simply <em>use</em> eggs, as opposed to building them.)</p> <p>Finally, in addition to providing access to eggs built via setuptools or other packaging tools, it should be noted that since Python 2.5, the distutils install package metadata (aka <code class="docutils literal notranslate"><span class="pre">PKG-INFO</span></code>) files that can be read by <code class="docutils literal notranslate"><span class="pre">pkg_resources</span></code> to identify what distributions are already on <code class="docutils literal notranslate"><span class="pre">sys.path</span></code>. In environments where Python packages are installed using system package tools (like RPM), the <code class="docutils literal notranslate"><span class="pre">pkg_resources</span></code> module provides an API for detecting what versions of what packages are installed, even if those packages were installed via the distutils instead of setuptools.</p> </section> <section id="implementation-and-documentation"> <h2><a class="toc-backref" href="#implementation-and-documentation" role="doc-backlink">Implementation and Documentation</a></h2> <p>The <code class="docutils literal notranslate"><span class="pre">pkg_resources</span></code> implementation is maintained in the Python SVN repository under <code class="docutils literal notranslate"><span class="pre">/sandbox/trunk/setuptools/</span></code>; see <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 egg format(s) supported by <code class="docutils literal notranslate"><span class="pre">pkg_resources</span></code> can be found in <code class="docutils literal notranslate"><span class="pre">doc/formats.txt</span></code>. HTML versions of these documents are available at:</p> <ul class="simple"> <li><a class="reference external" href="http://peak.telecommunity.com/DevCenter/PkgResources">http://peak.telecommunity.com/DevCenter/PkgResources</a> and</li> <li><a class="reference external" href="http://peak.telecommunity.com/DevCenter/EggFormats">http://peak.telecommunity.com/DevCenter/EggFormats</a></li> </ul> <p>(These HTML versions are for setuptools 0.6; they may not reflect all of the changes found in the Subversion trunk’s <code class="docutils literal notranslate"><span class="pre">.txt</span></code> versions.)</p> </section> <section id="copyright"> <h2><a class="toc-backref" href="#copyright" role="doc-backlink">Copyright</a></h2> <p>This document has been placed in the public domain.</p> </section> </section> <hr class="docutils" /> <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> <p>Last modified: <a class="reference external" href="https://github.com/python/peps/commits/main/peps/pep-0365.rst">2025-02-01 08:59:27 GMT</a></p> </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="#proposal">Proposal</a></li> <li><a class="reference internal" href="#rationale">Rationale</a></li> <li><a class="reference internal" href="#implementation-and-documentation">Implementation and Documentation</a></li> <li><a class="reference internal" href="#copyright">Copyright</a></li> </ul> <br> <a id="source" href="https://github.com/python/peps/blob/main/peps/pep-0365.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>