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<!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 666 – Reject Foolish Indentation | peps.python.org</title> <link rel="shortcut icon" href="../_static/py.png"> <link rel="canonical" href="https://peps.python.org/pep-0666/"> <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 666 – Reject Foolish Indentation | peps.python.org'> <meta property="og:description" content="Everybody agrees that mixing tabs and spaces is a bad idea. 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I propose that we let people define whatever Python behaviour they want, so it will only run the way they like it, and will not run the way they don’t like it..."> <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 666</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 666 – Reject Foolish Indentation</h1> <dl class="rfc2822 field-list simple"> <dt class="field-odd">Author<span class="colon">:</span></dt> <dd class="field-odd">Laura Creighton <lac at strakt.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">Created<span class="colon">:</span></dt> <dd class="field-even">03-Dec-2001</dd> <dt class="field-odd">Python-Version<span class="colon">:</span></dt> <dd class="field-odd">2.2</dd> <dt class="field-even">Post-History<span class="colon">:</span></dt> <dd class="field-even">05-Dec-2001</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="#references">References</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>Everybody agrees that mixing tabs and spaces is a bad idea. Some people want more than this. I propose that we let people define whatever Python behaviour they want, so it will only run the way they like it, and will not run the way they don’t like it. We will do this with a command line switch. Programs that aren’t formatted the way the programmer wants things will raise <code class="docutils literal notranslate"><span class="pre">IndentationError</span></code>.</p> <ul class="simple"> <li><code class="docutils literal notranslate"><span class="pre">python</span> <span class="pre">-TNone</span></code> will refuse to run when there are any tabs.</li> <li><code class="docutils literal notranslate"><span class="pre">python</span> <span class="pre">-Tn</span></code> will refuse to run when tabs are not exactly <code class="docutils literal notranslate"><span class="pre">n</span></code> spaces</li> <li><code class="docutils literal notranslate"><span class="pre">python</span> <span class="pre">-TOnly</span></code> will refuse to run when blocks are indented by anything other than tabs</li> </ul> <p>People who mix tabs and spaces, naturally, will find that their programs do not run. Alas, we haven’t found a way to give them an electric shock as from a cattle prod remotely. (Though if somebody finds out a way to do this, I will be pleased to add this option to the PEP.)</p> </section> <section id="rationale"> <h2><a class="toc-backref" href="#rationale" role="doc-backlink">Rationale</a></h2> <p><a class="reference external" href="mailto:Python-list%40python.org">Python-list<span>@</span>python<span>.</span>org</a> (a.k.a. comp.lang.python) is periodically awash with discussions about tabs and spaces. This is inevitable, given that indentation is syntactically significant in Python. This has never solved anything, and just makes various people frustrated and angry. Eventually they start saying rude things to each other which is sad for all of us. And it is also sad that they are wasting their valuable time which they could spend creating something with Python. Moreover, for the Python community as a whole, from a public relations point of view, this is quite unfortunate. The people who aren’t posting about tabs and spaces, are, (unsurprisingly) invisible, while the people who are posting make the rest of us look somewhat foolish.</p> <p>The problem is that there is no polite way to say ‘Stop wasting your valuable time and mine.’ People who are already in the middle of a flame war are not well disposed to believe that you are acting out of compassion for them, and quite rightly insist that their own time is their own to do with as they please. They are stuck like flies in treacle in this wretched argument, and it is self-evident that they cannot disengage or they would have already done so.</p> <p>But today I had to spend time cleaning my keyboard because the ‘n’ key is sticking. So, in addition to feeling compassion for these people, I am pretty annoyed. I figure if I make this PEP, we can then ask Guido to quickly reject it, and then when this argument next starts up again, we can say ‘Guido isn’t changing things to suit the tab-haters or the only-tabbers, so this conversation is a waste of time.’ Then everybody can quietly believe that a) they are correct and b) other people are fools and c) they are undeniably fortunate to not have to share a lab with idiots, (which is something the arguers could do _now_, but apparently have forgotten).</p> <p>And python-list can go back to worrying if it is too smug, rather than whether it is too hostile for newcomers. Possibly somebody could get around to explaining to me what is the difference between <code class="docutils literal notranslate"><span class="pre">__getattr__</span></code> and <code class="docutils literal notranslate"><span class="pre">__getattribute__</span></code> in non-Classic classes in 2.2, a question I have foolishly posted in the middle of the current tab thread. I would like to know the answer to that question <a class="footnote-reference brackets" href="#id2" id="id1">[1]</a>.</p> <p>This proposal, if accepted, will probably mean a heck of a lot of work for somebody. But since I don’t want it accepted, I don’t care.</p> </section> <section id="references"> <h2><a class="toc-backref" href="#references" role="doc-backlink">References</a></h2> <aside class="footnote-list brackets"> <aside class="footnote brackets" id="id2" role="doc-footnote"> <dt class="label" id="id2">[<a href="#id1">1</a>]</dt> <dd>Tim Peters already has (private correspondence). My early 2.2 didn’t have a <code class="docutils literal notranslate"><span class="pre">__getattribute__</span></code>, and <code class="docutils literal notranslate"><span class="pre">__getattr__</span></code> was implemented like <code class="docutils literal notranslate"><span class="pre">__getattribute__</span></code> now is. This has been fixed. The important conclusion is that my Decorator Pattern is safe and all is right with the world.</aside> </aside> </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-0666.rst">https://github.com/python/peps/blob/main/peps/pep-0666.rst</a></p> <p>Last modified: <a class="reference external" href="https://github.com/python/peps/commits/main/peps/pep-0666.rst">2025-02-01 08:55:40 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="#references">References</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-0666.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>