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bpo-35833: Revise IDLE doc for control codes sent to Shell. (GH-11799)

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Add  a code example block.
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Terry Jan Reedy 2019-02-08 22:51:51 -05:00 • committed by GitHub
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@ -6,7 +6,7 @@
<head>
<meta http-equiv="X-UA-Compatible" content="IE=Edge" />
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>IDLE &#8212; Python 3.8.0a0 documentation</title>
<title>IDLE &#8212; Python 3.8.0a1 documentation</title>
<link rel="stylesheet" href="../_static/pydoctheme.css" type="text/css" />
<link rel="stylesheet" href="../_static/pygments.css" type="text/css" />
@ -19,7 +19,7 @@
<script type="text/javascript" src="../_static/sidebar.js"></script>
<link rel="search" type="application/opensearchdescription+xml"
title="Search within Python 3.8.0a0 documentation"
title="Search within Python 3.8.0a1 documentation"
href="../_static/opensearch.xml"/>
<link rel="author" title="About these documents" href="../about.html" />
<link rel="index" title="Index" href="../genindex.html" />
@ -72,7 +72,7 @@
<li>
<a href="../index.html">3.8.0a0 Documentation</a> &#187;
<a href="../index.html">3.8.0a1 Documentation</a> &#187;
</li>
<li class="nav-item nav-item-1"><a href="index.html" >The Python Standard Library</a> &#187;</li>
@ -673,14 +673,31 @@ output to Shell will eventually fill memory, resulting in a memory error.
In contrast, some system text windows only keep the last n lines of output.
A Windows console, for instance, keeps a user-settable 1 to 9999 lines,
with 300 the default.</p>
<p>Text widgets display a subset of Unicode, the Basic Multilingual Plane (BMP).
Which characters get a proper glyph instead of a replacement box depends on
the operating system and installed fonts. Newline characters cause following
text to appear on a new line, but other control characters are either
replaced with a box or deleted. However, <code class="docutils literal notranslate"><span class="pre">repr()</span></code>, which is used for
interactive echo of expression values, replaces control characters,
some BMP codepoints, and all non-BMP characters with escape codes
before they are output.</p>
<p>A Tk Text widget, and hence IDLE’s Shell, displays characters (codepoints)
in the the BMP (Basic Multilingual Plane) subset of Unicode.
Which characters are displayed with a proper glyph and which with a
replacement box depends on the operating system and installed fonts.
Tab characters cause the following text to begin after
the next tab stop. (They occur every 8 ‘characters’).
Newline characters cause following text to appear on a new line.
Other control characters are ignored or displayed as a space, box, or
something else, depending on the operating system and font.
(Moving the text cursor through such output with arrow keys may exhibit
some surprising spacing behavior.)</p>
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span>&gt;&gt;&gt; s = &#39;a\tb\a&lt;\x02&gt;&lt;\r&gt;\bc\nd&#39;
&gt;&gt;&gt; len(s)
14
&gt;&gt;&gt; s # Display repr(s)
&#39;a\tb\x07&lt;\x02&gt;&lt;\r&gt;\x08c\nd&#39;
&gt;&gt;&gt; print(s, end=&#39;&#39;) # Display s as is.
# Result varies by OS and font. Try it.
</pre></div>
</div>
<p>The <code class="docutils literal notranslate"><span class="pre">repr</span></code> function is used for interactive echo of expression
values. It returns an altered version of the input string in which
control codes, some BMP codepoints, and all non-BMP codepoints are
replaced with escape codes. As demonstrated above, it allows one to
identify the characters in a string, regardless of how they are displayed.</p>
<p>Normal and error output are generally kept separate (on separate lines)
from code input and each other. They each get different highlight colors.</p>
<p>For SyntaxError tracebacks, the normal ‘^’ marking where the error was
@ -889,7 +906,7 @@ also used for testing.</p>
<li>
<a href="../index.html">3.8.0a0 Documentation</a> &#187;
<a href="../index.html">3.8.0a1 Documentation</a> &#187;
</li>
<li class="nav-item nav-item-1"><a href="index.html" >The Python Standard Library</a> &#187;</li>
@ -912,7 +929,7 @@ also used for testing.</p>
</ul>
</div>
<div class="footer">
&copy; <a href="../copyright.html">Copyright</a> 2001-2018, Python Software Foundation.
&copy; <a href="../copyright.html">Copyright</a> 2001-2019, Python Software Foundation.
<br />
The Python Software Foundation is a non-profit corporation.
@ -920,7 +937,7 @@ also used for testing.</p>
<br />
<br />
Last updated on Dec 28, 2018.
Last updated on Feb 08, 2019.
<a href="https://docs.python.org/3/bugs.html">Found a bug</a>?
<br />