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<h1>Python Enhancement Proposals</h1>
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<li><a href="https://www.python.org/" title="The Python Programming Language">Python</a> » </li>
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<li><a href="../pep-0000/">PEP Index</a> » </li>
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<h1 class="page-title">PEP 216 – Docstring Format</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">Moshe Zadka <moshez at zadka.site.co.il></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="Non-normative PEP containing background, guidelines or other information relevant to the Python ecosystem">Informational</abbr></dd>
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<dt class="field-even">Created<span class="colon">:</span></dt>
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<dd class="field-even">31-Jul-2000</dd>
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<dt class="field-odd">Post-History<span class="colon">:</span></dt>
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<dd class="field-odd"><p></p></dd>
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<dt class="field-even">Superseded-By<span class="colon">:</span></dt>
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<dd class="field-even"><a class="reference external" href="../pep-0287/">287</a></dd>
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</dl>
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<section id="contents">
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<details><summary>Table of Contents</summary><ul class="simple">
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<li><a class="reference internal" href="#notice">Notice</a></li>
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<li><a class="reference internal" href="#abstract">Abstract</a></li>
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<li><a class="reference internal" href="#perl-documentation">Perl Documentation</a></li>
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<li><a class="reference internal" href="#java-documentation">Java Documentation</a></li>
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<li><a class="reference internal" href="#python-docstring-goals">Python Docstring Goals</a></li>
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<li><a class="reference internal" href="#high-level-solutions">High Level Solutions</a></li>
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<li><a class="reference internal" href="#docstring-format-goals">Docstring Format Goals</a></li>
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<li><a class="reference internal" href="#docstring-contents">Docstring Contents</a></li>
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<li><a class="reference internal" href="#docstring-basic-structure">Docstring Basic Structure</a></li>
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<li><a class="reference internal" href="#unresolved-issues">Unresolved Issues</a></li>
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<li><a class="reference internal" href="#rejected-suggestions">Rejected Suggestions</a></li>
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</ul>
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</details></section>
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<section id="notice">
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<h2><a class="toc-backref" href="#notice" role="doc-backlink">Notice</a></h2>
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<p>This PEP is rejected by the author. It has been superseded by PEP
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287.</p>
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</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>Named Python objects, such as modules, classes and functions, have a
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string attribute called <code class="docutils literal notranslate"><span class="pre">__doc__</span></code>. If the first expression inside
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the definition is a literal string, that string is assigned
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to the <code class="docutils literal notranslate"><span class="pre">__doc__</span></code> attribute.</p>
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<p>The <code class="docutils literal notranslate"><span class="pre">__doc__</span></code> attribute is called a documentation string, or docstring.
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It is often used to summarize the interface of the module, class or
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function. However, since there is no common format for documentation
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string, tools for extracting docstrings and transforming those into
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documentation in a standard format (e.g., DocBook) have not sprang
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up in abundance, and those that do exist are for the most part
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unmaintained and unused.</p>
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</section>
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<section id="perl-documentation">
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<h2><a class="toc-backref" href="#perl-documentation" role="doc-backlink">Perl Documentation</a></h2>
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<p>In Perl, most modules are documented in a format called POD – Plain
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Old Documentation. This is an easy-to-type, very low level format
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which integrates well with the Perl parser. Many tools exist to turn
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POD documentation into other formats: info, HTML and man pages, among
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others. However, in Perl, the information is not available at run-time.</p>
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</section>
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<section id="java-documentation">
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<h2><a class="toc-backref" href="#java-documentation" role="doc-backlink">Java Documentation</a></h2>
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<p>In Java, special comments before classes and functions function to
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document the code. A program to extract these, and turn them into
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HTML documentation is called javadoc, and is part of the standard
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Java distribution. However, the only output format that is supported
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is HTML, and JavaDoc has a very intimate relationship with HTML.</p>
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</section>
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<section id="python-docstring-goals">
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<h2><a class="toc-backref" href="#python-docstring-goals" role="doc-backlink">Python Docstring Goals</a></h2>
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<p>Python documentation string are easy to spot during parsing, and are
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also available to the runtime interpreter. This double purpose is
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a bit problematic, sometimes: for example, some are reluctant to have
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too long docstrings, because they do not want to take much space in
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the runtime. In addition, because of the current lack of tools, people
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read objects’ docstrings by “print”ing them, so a tendency to make them
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brief and free of markups has sprung up. This tendency hinders writing
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better documentation-extraction tools, since it causes docstrings to
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contain little information, which is hard to parse.</p>
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</section>
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<section id="high-level-solutions">
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<h2><a class="toc-backref" href="#high-level-solutions" role="doc-backlink">High Level Solutions</a></h2>
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<p>To counter the objection that the strings take up place in the running
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program, it is suggested that documentation extraction tools will
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concatenate a maximum prefix of string literals which appear in the
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beginning of a definition. The first of these will also be available
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in the interactive interpreter, so it should contain a few summary
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lines.</p>
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</section>
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<section id="docstring-format-goals">
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<h2><a class="toc-backref" href="#docstring-format-goals" role="doc-backlink">Docstring Format Goals</a></h2>
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<p>These are the goals for the docstring format, as discussed ad nauseam
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in the doc-sig.</p>
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<ol class="arabic simple">
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<li>It must be easy to type with any standard text editor.</li>
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<li>It must be readable to the casual observer.</li>
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<li>It must not contain information which can be deduced from parsing
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the module.</li>
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<li>It must contain sufficient information so it can be converted
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to any reasonable markup format.</li>
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<li>It must be possible to write a module’s entire documentation in
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docstrings, without feeling hampered by the markup language.</li>
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</ol>
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</section>
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<section id="docstring-contents">
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<h2><a class="toc-backref" href="#docstring-contents" role="doc-backlink">Docstring Contents</a></h2>
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<p>For requirement 5. above, it is needed to specify what must be
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in docstrings.</p>
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<p>At least the following must be available:</p>
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<ol class="loweralpha">
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<li>A tag that means “this is a Python <em>something</em>, guess what”<p>Example: In the sentence “The POP3 class”, we need to markup “POP3”
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so. The parser will be able to guess it is a class from the contents
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of the <code class="docutils literal notranslate"><span class="pre">poplib</span></code> module, but we need to make it guess.</p>
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</li>
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<li>Tags that mean “this is a Python class/module/class var/instance var…”<p>Example: The usual Python idiom for singleton class <code class="docutils literal notranslate"><span class="pre">A</span></code> is to have <code class="docutils literal notranslate"><span class="pre">_A</span></code>
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as the class, and <code class="docutils literal notranslate"><span class="pre">A</span></code> a function which returns <code class="docutils literal notranslate"><span class="pre">_A</span></code> objects. It’s usual
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to document the class, nonetheless, as being <code class="docutils literal notranslate"><span class="pre">A</span></code>. This requires the
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strength to say “The class <code class="docutils literal notranslate"><span class="pre">A</span></code>” and have <code class="docutils literal notranslate"><span class="pre">A</span></code> hyperlinked and marked-up
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as a class.</p>
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</li>
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<li>An easy way to include Python source code/Python interactive sessions</li>
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<li>Emphasis/bold</li>
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<li>List/tables</li>
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</ol>
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</section>
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<section id="docstring-basic-structure">
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<h2><a class="toc-backref" href="#docstring-basic-structure" role="doc-backlink">Docstring Basic Structure</a></h2>
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<p>The documentation strings will be in StructuredTextNG
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(<a class="reference external" href="http://www.zope.org/Members/jim/StructuredTextWiki/StructuredTextNG">http://www.zope.org/Members/jim/StructuredTextWiki/StructuredTextNG</a>)
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Since StructuredText is not yet strong enough to handle (a) and (b)
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above, we will need to extend it. I suggest using
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<code class="docutils literal notranslate"><span class="pre">[<optional</span> <span class="pre">description>:python</span> <span class="pre">identifier]</span></code>.
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E.g.: <code class="docutils literal notranslate"><span class="pre">[class:POP3]</span></code>, <code class="docutils literal notranslate"><span class="pre">[:POP3.list]</span></code>, etc. If the description is missing,
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a guess will be made from the text.</p>
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</section>
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<section id="unresolved-issues">
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<h2><a class="toc-backref" href="#unresolved-issues" role="doc-backlink">Unresolved Issues</a></h2>
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<p>Is there a way to escape characters in ST? If so, how?
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(example: * at the beginning of a line without being bullet symbol)</p>
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<p>Is my suggestion above for Python symbols compatible with ST-NG?
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How hard would it be to extend ST-NG to support it?</p>
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<p>How do we describe input and output types of functions?</p>
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<p>What additional constraint do we enforce on each docstring?
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(module/class/function)?</p>
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<p>What are the guesser rules?</p>
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</section>
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<section id="rejected-suggestions">
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<h2><a class="toc-backref" href="#rejected-suggestions" role="doc-backlink">Rejected Suggestions</a></h2>
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<p>XML – it’s very hard to type, and too cluttered to read it comfortably.</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-0216.rst">https://github.com/python/peps/blob/main/peps/pep-0216.rst</a></p>
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<p>Last modified: <a class="reference external" href="https://github.com/python/peps/commits/main/peps/pep-0216.rst">2023-09-09 17:39:29 GMT</a></p>
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</article>
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<h2>Contents</h2>
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<ul>
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<li><a class="reference internal" href="#notice">Notice</a></li>
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<li><a class="reference internal" href="#abstract">Abstract</a></li>
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<li><a class="reference internal" href="#perl-documentation">Perl Documentation</a></li>
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<li><a class="reference internal" href="#java-documentation">Java Documentation</a></li>
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<li><a class="reference internal" href="#python-docstring-goals">Python Docstring Goals</a></li>
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<li><a class="reference internal" href="#high-level-solutions">High Level Solutions</a></li>
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<li><a class="reference internal" href="#docstring-format-goals">Docstring Format Goals</a></li>
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<li><a class="reference internal" href="#docstring-contents">Docstring Contents</a></li>
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<li><a class="reference internal" href="#docstring-basic-structure">Docstring Basic Structure</a></li>
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<li><a class="reference internal" href="#unresolved-issues">Unresolved Issues</a></li>
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<li><a class="reference internal" href="#rejected-suggestions">Rejected Suggestions</a></li>
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</ul>
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