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<h1 class="page-title">PEP 3003 – Python Language Moratorium</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">Brett Cannon, Jesse Noller, Guido van Rossum</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abbr title="Accepted and implementation complete, or no longer active">Final</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 describing or proposing a change to a Python community process, workflow or governance">Process</abbr></dd>
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<dt class="field-even">Created<span class="colon">:</span></dt>
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<dd class="field-even">21-Oct-2009</dd>
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<dt class="field-odd">Post-History<span class="colon">:</span></dt>
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<dd class="field-odd">03-Nov-2009</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="#rationale">Rationale</a></li>
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<li><a class="reference internal" href="#details">Details</a><ul>
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<li><a class="reference internal" href="#cannot-change">Cannot Change</a></li>
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<li><a class="reference internal" href="#case-by-case-exemptions">Case-by-Case Exemptions</a></li>
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<li><a class="reference internal" href="#allowed-to-change">Allowed to Change</a></li>
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</ul>
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</li>
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<li><a class="reference internal" href="#retroactive">Retroactive</a></li>
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<li><a class="reference internal" href="#extensions">Extensions</a></li>
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<li><a class="reference internal" href="#copyright">Copyright</a></li>
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<li><a class="reference internal" href="#references">References</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 a temporary moratorium (suspension) of all changes
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to the Python language syntax, semantics, and built-ins for a period
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of at least two years from the release of Python 3.1. In particular, the
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moratorium would include Python 3.2 (to be released 18-24 months after
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3.1) but allow Python 3.3 (assuming it is not released prematurely) to
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once again include language changes.</p>
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<p>This suspension of features is designed to allow non-CPython implementations
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to “catch up” to the core implementation of the language, help ease adoption
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of Python 3.x, and provide a more stable base for the community.</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>This idea was proposed by Guido van Rossum on the python-ideas <a class="footnote-reference brackets" href="#id6" id="id1">[1]</a> mailing
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list. The premise of his email was to slow the alteration of the Python core
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syntax, builtins and semantics to allow non-CPython implementations to catch
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up to the current state of Python, both 2.x and 3.x.</p>
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<p>Python, as a language is more than the core implementation –
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CPython – with a rich, mature and vibrant community of implementations, such
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as Jython <a class="footnote-reference brackets" href="#id7" id="id2">[2]</a>, IronPython <a class="footnote-reference brackets" href="#id8" id="id3">[3]</a> and PyPy <a class="footnote-reference brackets" href="#id9" id="id4">[4]</a> that are a benefit not only to
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the community, but to the language itself.</p>
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<p>Still others, such as Unladen Swallow <a class="footnote-reference brackets" href="#id10" id="id5">[5]</a> (a branch of CPython) seek not to
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create an alternative implementation, but rather they seek to enhance the
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performance and implementation of CPython itself.</p>
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<p>Python 3.x was a large part of the last several years of Python’s
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development. Its release, as well as a bevy of changes to the language
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introduced by it and the previous 2.6.x releases, puts alternative
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implementations at a severe disadvantage in “keeping pace” with core python
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development.</p>
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<p>Additionally, many of the changes put into the recent releases of the language
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as implemented by CPython have not yet seen widespread usage by the
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general user population. For example, most users are limited to the version
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of the interpreter (typically CPython) which comes pre-installed with their
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operating system. Most OS vendors are just barely beginning to ship Python 2.6
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– even fewer are shipping Python 3.x.</p>
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<p>As it is expected that Python 2.7 be the effective “end of life” of the Python
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2.x code line, with Python 3.x being the future, it is in the best interest of
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Python core development to temporarily suspend the alteration of the language
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itself to allow all of these external entities to catch up and to assist in
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the adoption of, and migration to, Python 3.x</p>
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<p>Finally, the moratorium is intended to free up cycles within core development
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to focus on other issues, such as the CPython interpreter and improvements
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therein, the standard library, etc.</p>
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<p>This moratorium does not allow for exceptions – once accepted, any pending
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changes to the syntax or semantics of the language will be postponed until the
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moratorium is lifted.</p>
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<p>This moratorium does not attempt to apply to any other Python implementation
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meaning that if desired other implementations may add features which deviate
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||
from the standard implementation.</p>
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</section>
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<section id="details">
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<h2><a class="toc-backref" href="#details" role="doc-backlink">Details</a></h2>
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<section id="cannot-change">
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<h3><a class="toc-backref" href="#cannot-change" role="doc-backlink">Cannot Change</a></h3>
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<ul class="simple">
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<li>New built-ins</li>
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<li><dl class="simple">
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<dt>Language syntax</dt><dd>The grammar file essentially becomes immutable apart from ambiguity
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fixes.</dd>
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</dl>
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</li>
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<li><dl class="simple">
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<dt>General language semantics</dt><dd>The language operates as-is with only specific exemptions (see
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below).</dd>
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</dl>
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</li>
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<li><dl class="simple">
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<dt>New __future__ imports</dt><dd>These are explicitly forbidden, as they effectively change the language
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syntax and/or semantics (albeit using a compiler directive).</dd>
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</dl>
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</li>
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</ul>
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</section>
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<section id="case-by-case-exemptions">
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<h3><a class="toc-backref" href="#case-by-case-exemptions" role="doc-backlink">Case-by-Case Exemptions</a></h3>
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<ul class="simple">
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<li><dl class="simple">
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<dt>New methods on built-ins</dt><dd>The case for adding a method to a built-in object can be made.</dd>
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||
</dl>
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</li>
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<li><dl class="simple">
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||
<dt>Incorrect language semantics</dt><dd>If the language semantics turn out to be ambiguous or improperly
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||
implemented based on the intention of the original design then the
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||
semantics may change.</dd>
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</dl>
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</li>
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<li><dl class="simple">
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<dt>Language semantics that are difficult to implement</dt><dd>Because other VMs have not begun implementing Python 3.x semantics
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there is a possibility that certain semantics are too difficult to
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||
replicate. In those cases they can be changed to ease adoption of
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||
Python 3.x by the other VMs.</dd>
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</dl>
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</li>
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</ul>
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</section>
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<section id="allowed-to-change">
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<h3><a class="toc-backref" href="#allowed-to-change" role="doc-backlink">Allowed to Change</a></h3>
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<ul class="simple">
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<li><dl class="simple">
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<dt>C API</dt><dd>It is entirely acceptable to change the underlying C code of
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CPython as long as other restrictions of this moratorium are not
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broken. E.g. removing the GIL would be fine assuming certain
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||
operations that are currently atomic remain atomic.</dd>
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</dl>
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</li>
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<li><dl class="simple">
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<dt>The standard library</dt><dd>As the standard library is not directly tied to the language
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definition it is not covered by this moratorium.</dd>
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</dl>
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</li>
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<li><dl class="simple">
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<dt>Backports of 3.x features to 2.x</dt><dd>The moratorium only affects features that would be new in 3.x.</dd>
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</dl>
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</li>
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<li><dl class="simple">
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<dt>Import semantics</dt><dd>For example, <a class="pep reference internal" href="../pep-0382/" title="PEP 382 – Namespace Packages">PEP 382</a>. After all, import semantics vary between
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||
Python implementations anyway.</dd>
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</dl>
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</li>
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</ul>
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</section>
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</section>
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<section id="retroactive">
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<h2><a class="toc-backref" href="#retroactive" role="doc-backlink">Retroactive</a></h2>
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<p>It is important to note that the moratorium covers all changes since the release
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||
of Python 3.1. This rule is intended to avoid features being rushed or smuggled
|
||
into the CPython source tree while the moratorium is being discussed. A review
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||
of the NEWS file for the py3k development branch showed no commits would need to
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||
be rolled back in order to meet this goal.</p>
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</section>
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<section id="extensions">
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<h2><a class="toc-backref" href="#extensions" role="doc-backlink">Extensions</a></h2>
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<p>The time period of the moratorium can only be extended through a new PEP.</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>
|
||
<p>This document has been placed in the public domain.</p>
|
||
</section>
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<section id="references">
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<h2><a class="toc-backref" href="#references" role="doc-backlink">References</a></h2>
|
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<aside class="footnote-list brackets">
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<aside class="footnote brackets" id="id6" role="doc-footnote">
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<dt class="label" id="id6">[<a href="#id1">1</a>]</dt>
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||
<dd><a class="reference external" href="https://mail.python.org/pipermail/python-ideas/2009-October/006305.html">https://mail.python.org/pipermail/python-ideas/2009-October/006305.html</a></aside>
|
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<aside class="footnote brackets" id="id7" role="doc-footnote">
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<dt class="label" id="id7">[<a href="#id2">2</a>]</dt>
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<dd><a class="reference external" href="http://www.jython.org/">http://www.jython.org/</a></aside>
|
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<aside class="footnote brackets" id="id8" role="doc-footnote">
|
||
<dt class="label" id="id8">[<a href="#id3">3</a>]</dt>
|
||
<dd><a class="reference external" href="http://www.codeplex.com/IronPython">http://www.codeplex.com/IronPython</a></aside>
|
||
<aside class="footnote brackets" id="id9" role="doc-footnote">
|
||
<dt class="label" id="id9">[<a href="#id4">4</a>]</dt>
|
||
<dd><a class="reference external" href="http://codespeak.net/pypy/">http://codespeak.net/pypy/</a></aside>
|
||
<aside class="footnote brackets" id="id10" role="doc-footnote">
|
||
<dt class="label" id="id10">[<a href="#id5">5</a>]</dt>
|
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<dd><a class="reference external" href="http://code.google.com/p/unladen-swallow/">http://code.google.com/p/unladen-swallow/</a></aside>
|
||
</aside>
|
||
</section>
|
||
</section>
|
||
<hr class="docutils" />
|
||
<p>Source: <a class="reference external" href="https://github.com/python/peps/blob/main/peps/pep-3003.rst">https://github.com/python/peps/blob/main/peps/pep-3003.rst</a></p>
|
||
<p>Last modified: <a class="reference external" href="https://github.com/python/peps/commits/main/peps/pep-3003.rst">2023-09-09 17:39:29 GMT</a></p>
|
||
|
||
</article>
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||
<nav id="pep-sidebar">
|
||
<h2>Contents</h2>
|
||
<ul>
|
||
<li><a class="reference internal" href="#abstract">Abstract</a></li>
|
||
<li><a class="reference internal" href="#rationale">Rationale</a></li>
|
||
<li><a class="reference internal" href="#details">Details</a><ul>
|
||
<li><a class="reference internal" href="#cannot-change">Cannot Change</a></li>
|
||
<li><a class="reference internal" href="#case-by-case-exemptions">Case-by-Case Exemptions</a></li>
|
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<li><a class="reference internal" href="#allowed-to-change">Allowed to Change</a></li>
|
||
</ul>
|
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</li>
|
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<li><a class="reference internal" href="#retroactive">Retroactive</a></li>
|
||
<li><a class="reference internal" href="#extensions">Extensions</a></li>
|
||
<li><a class="reference internal" href="#copyright">Copyright</a></li>
|
||
<li><a class="reference internal" href="#references">References</a></li>
|
||
</ul>
|
||
|
||
<br>
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<a id="source" href="https://github.com/python/peps/blob/main/peps/pep-3003.rst">Page Source (GitHub)</a>
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