231 lines
14 KiB
HTML
231 lines
14 KiB
HTML
|
||
<!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 295 – Interpretation of multiline string constants | peps.python.org</title>
|
||
<link rel="shortcut icon" href="../_static/py.png">
|
||
<link rel="canonical" href="https://peps.python.org/pep-0295/">
|
||
<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 295 – Interpretation of multiline string constants | peps.python.org'>
|
||
<meta property="og:description" content="This PEP describes an interpretation of multiline string constants for Python. It suggests stripping spaces after newlines and stripping a newline if it is first character after an opening quotation.">
|
||
<meta property="og:type" content="website">
|
||
<meta property="og:url" content="https://peps.python.org/pep-0295/">
|
||
<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 describes an interpretation of multiline string constants for Python. It suggests stripping spaces after newlines and stripping a newline if it is first character after an opening quotation.">
|
||
<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 295</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 295 – Interpretation of multiline string constants</h1>
|
||
<dl class="rfc2822 field-list simple">
|
||
<dt class="field-odd">Author<span class="colon">:</span></dt>
|
||
<dd class="field-odd">Stepan Koltsov <yozh at mx1.ru></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">Created<span class="colon">:</span></dt>
|
||
<dd class="field-even">22-Jul-2002</dd>
|
||
<dt class="field-odd">Python-Version<span class="colon">:</span></dt>
|
||
<dd class="field-odd">3.0</dd>
|
||
<dt class="field-even">Post-History<span class="colon">:</span></dt>
|
||
<dd class="field-even"><p></p></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="#rationale">Rationale</a></li>
|
||
<li><a class="reference internal" href="#implementation">Implementation</a></li>
|
||
<li><a class="reference internal" href="#alternatives">Alternatives</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 describes an interpretation of multiline string constants
|
||
for Python. It suggests stripping spaces after newlines and
|
||
stripping a newline if it is first character after an opening
|
||
quotation.</p>
|
||
</section>
|
||
<section id="rationale">
|
||
<h2><a class="toc-backref" href="#rationale" role="doc-backlink">Rationale</a></h2>
|
||
<p>This PEP proposes an interpretation of multiline string constants
|
||
in Python. Currently, the value of string constant is all the
|
||
text between quotations, maybe with escape sequences substituted,
|
||
e.g.:</p>
|
||
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="k">def</span> <span class="nf">f</span><span class="p">():</span>
|
||
<span class="w"> </span><span class="sd">"""</span>
|
||
<span class="sd"> la-la-la</span>
|
||
<span class="sd"> limona, banana</span>
|
||
<span class="sd"> """</span>
|
||
|
||
<span class="k">def</span> <span class="nf">g</span><span class="p">():</span>
|
||
<span class="k">return</span> <span class="s2">"This is </span><span class="se">\</span>
|
||
<span class="s2"> string"</span>
|
||
|
||
<span class="nb">print</span> <span class="nb">repr</span><span class="p">(</span><span class="n">f</span><span class="o">.</span><span class="vm">__doc__</span><span class="p">)</span>
|
||
<span class="nb">print</span> <span class="nb">repr</span><span class="p">(</span><span class="n">g</span><span class="p">())</span>
|
||
</pre></div>
|
||
</div>
|
||
<p>prints:</p>
|
||
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="s1">'</span><span class="se">\n\t</span><span class="s1">la-la-la</span><span class="se">\n\t</span><span class="s1">limona, banana</span><span class="se">\n\t</span><span class="s1">'</span>
|
||
<span class="s1">'This is </span><span class="se">\t</span><span class="s1">string'</span>
|
||
</pre></div>
|
||
</div>
|
||
<p>This PEP suggest two things:</p>
|
||
<ul class="simple">
|
||
<li>ignore the first character after opening quotation, if it is
|
||
newline</li>
|
||
<li>ignore in string constants all spaces and tabs up to
|
||
first non-whitespace character, but no more than current
|
||
indentation.</li>
|
||
</ul>
|
||
<p>After applying this, previous program will print:</p>
|
||
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="s1">'la-la-la</span><span class="se">\n</span><span class="s1">limona, banana</span><span class="se">\n</span><span class="s1">'</span>
|
||
<span class="s1">'This is string'</span>
|
||
</pre></div>
|
||
</div>
|
||
<p>To get this result, previous programs could be rewritten for
|
||
current Python as (note, this gives the same result with new
|
||
strings meaning):</p>
|
||
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="k">def</span> <span class="nf">f</span><span class="p">():</span>
|
||
<span class="w"> </span><span class="sd">"""\</span>
|
||
<span class="sd">la-la-la</span>
|
||
<span class="sd">limona, banana</span>
|
||
<span class="sd">"""</span>
|
||
|
||
<span class="k">def</span> <span class="nf">g</span><span class="p">():</span>
|
||
<span class="s2">"This is </span><span class="se">\</span>
|
||
<span class="s2">string"</span>
|
||
</pre></div>
|
||
</div>
|
||
<p>Or stripping can be done with library routines at runtime (as
|
||
pydoc does), but this decreases program readability.</p>
|
||
</section>
|
||
<section id="implementation">
|
||
<h2><a class="toc-backref" href="#implementation" role="doc-backlink">Implementation</a></h2>
|
||
<p>I’ll say nothing about CPython, Jython or Python.NET.</p>
|
||
<p>In original Python, there is no info about the current indentation
|
||
(in spaces) at compile time, so space and tab stripping should be
|
||
done at parse time. Currently no flags can be passed to the
|
||
parser in program text (like <code class="docutils literal notranslate"><span class="pre">from</span> <span class="pre">__future__</span> <span class="pre">import</span> <span class="pre">xxx</span></code>). I
|
||
suggest enabling or disabling of this feature at Python compile
|
||
time depending of CPP flag <code class="docutils literal notranslate"><span class="pre">Py_PARSE_MULTILINE_STRINGS</span></code>.</p>
|
||
</section>
|
||
<section id="alternatives">
|
||
<h2><a class="toc-backref" href="#alternatives" role="doc-backlink">Alternatives</a></h2>
|
||
<p>New interpretation of string constants can be implemented with flags
|
||
‘i’ and ‘o’ to string constants, like:</p>
|
||
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">i</span><span class="s2">"""</span>
|
||
<span class="s2">SELECT * FROM car</span>
|
||
<span class="s2">WHERE model = 'i525'</span>
|
||
<span class="s2">"""</span> <span class="ow">is</span> <span class="ow">in</span> <span class="n">new</span> <span class="n">style</span><span class="p">,</span>
|
||
|
||
<span class="n">o</span><span class="s2">"""SELECT * FROM employee</span>
|
||
<span class="s2">WHERE birth < 1982</span>
|
||
<span class="s2">"""</span> <span class="ow">is</span> <span class="ow">in</span> <span class="n">old</span> <span class="n">style</span><span class="p">,</span> <span class="ow">and</span>
|
||
|
||
<span class="sd">"""</span>
|
||
<span class="sd">SELECT employee.name, car.name, car.price FROM employee, car</span>
|
||
<span class="sd">WHERE employee.salary * 36 > car.price</span>
|
||
<span class="sd">"""</span> <span class="ow">is</span> <span class="ow">in</span> <span class="n">new</span> <span class="n">style</span> <span class="n">after</span> <span class="n">Python</span><span class="o">-</span><span class="n">x</span><span class="o">.</span><span class="n">y</span><span class="o">.</span><span class="n">z</span> <span class="ow">and</span> <span class="ow">in</span> <span class="n">old</span> <span class="n">style</span> <span class="n">otherwise</span><span class="o">.</span>
|
||
</pre></div>
|
||
</div>
|
||
<p>Also this feature can be disabled if string is raw, i.e. if flag ‘r’
|
||
specified.</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-0295.rst">https://github.com/python/peps/blob/main/peps/pep-0295.rst</a></p>
|
||
<p>Last modified: <a class="reference external" href="https://github.com/python/peps/commits/main/peps/pep-0295.rst">2023-09-09 17:39:29 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="#rationale">Rationale</a></li>
|
||
<li><a class="reference internal" href="#implementation">Implementation</a></li>
|
||
<li><a class="reference internal" href="#alternatives">Alternatives</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-0295.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> |