File: //usr/local/ssl/share/doc/python-docs-2.4.3/html/lib/differ-objects.html
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<html>
<head>
<link rel="STYLESHEET" href="lib.css" type='text/css' />
<link rel="SHORTCUT ICON" href="../icons/pyfav.png" type="image/png" />
<link rel='start' href='../index.html' title='Python Documentation Index' />
<link rel="first" href="lib.html" title='Python Library Reference' />
<link rel='contents' href='contents.html' title="Contents" />
<link rel='index' href='genindex.html' title='Index' />
<link rel='last' href='about.html' title='About this document...' />
<link rel='help' href='about.html' title='About this document...' />
<link rel="next" href="differ-examples.html" />
<link rel="prev" href="sequencematcher-examples.html" />
<link rel="parent" href="module-difflib.html" />
<link rel="next" href="differ-examples.html" />
<meta name='aesop' content='information' />
<title>4.4.3 Differ Objects </title>
</head>
<body>
<DIV CLASS="navigation">
<div id='top-navigation-panel' xml:id='top-navigation-panel'>
<table align="center" width="100%" cellpadding="0" cellspacing="2">
<tr>
<td class='online-navigation'><a rel="prev" title="4.4.2 SequenceMatcher Examples"
href="sequencematcher-examples.html"><img src='../icons/previous.png'
border='0' height='32' alt='Previous Page' width='32' /></A></td>
<td class='online-navigation'><a rel="parent" title="4.4 difflib "
href="module-difflib.html"><img src='../icons/up.png'
border='0' height='32' alt='Up One Level' width='32' /></A></td>
<td class='online-navigation'><a rel="next" title="4.4.4 Differ Example"
href="differ-examples.html"><img src='../icons/next.png'
border='0' height='32' alt='Next Page' width='32' /></A></td>
<td align="center" width="100%">Python Library Reference</td>
<td class='online-navigation'><a rel="contents" title="Table of Contents"
href="contents.html"><img src='../icons/contents.png'
border='0' height='32' alt='Contents' width='32' /></A></td>
<td class='online-navigation'><a href="modindex.html" title="Module Index"><img src='../icons/modules.png'
border='0' height='32' alt='Module Index' width='32' /></a></td>
<td class='online-navigation'><a rel="index" title="Index"
href="genindex.html"><img src='../icons/index.png'
border='0' height='32' alt='Index' width='32' /></A></td>
</tr></table>
<div class='online-navigation'>
<b class="navlabel">Previous:</b>
<a class="sectref" rel="prev" href="sequencematcher-examples.html">4.4.2 SequenceMatcher Examples</A>
<b class="navlabel">Up:</b>
<a class="sectref" rel="parent" href="module-difflib.html">4.4 difflib </A>
<b class="navlabel">Next:</b>
<a class="sectref" rel="next" href="differ-examples.html">4.4.4 Differ Example</A>
</div>
<hr /></div>
</DIV>
<!--End of Navigation Panel-->
<H2><A NAME="SECTION006430000000000000000"></A><A NAME="differ-objects"></A>
<BR>
4.4.3 Differ Objects
</H2>
<P>
Note that <tt class="class">Differ</tt>-generated deltas make no claim to be
<strong>minimal</strong> diffs. To the contrary, minimal diffs are often
counter-intuitive, because they synch up anywhere possible, sometimes
accidental matches 100 pages apart. Restricting synch points to
contiguous matches preserves some notion of locality, at the
occasional cost of producing a longer diff.
<P>
The <tt class="class">Differ</tt> class has this constructor:
<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
<td><nobr><b><span class="typelabel">class</span> <tt id='l2h-947' xml:id='l2h-947' class="class">Differ</tt></b>(</nobr></td>
<td><var></var><big>[</big><var>linejunk</var><big>[</big><var>, charjunk</var><big>]</big><var></var><big>]</big><var></var>)</td></tr></table></dt>
<dd>
Optional keyword parameters <var>linejunk</var> and <var>charjunk</var> are
for filter functions (or <code>None</code>):
<P>
<var>linejunk</var>: A function that accepts a single string
argument, and returns true if the string is junk. The default is
<code>None</code>, meaning that no line is considered junk.
<P>
<var>charjunk</var>: A function that accepts a single character argument
(a string of length 1), and returns true if the character is junk.
The default is <code>None</code>, meaning that no character is
considered junk.
</dl>
<P>
<tt class="class">Differ</tt> objects are used (deltas generated) via a single
method:
<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
<td><nobr><b><tt id='l2h-948' xml:id='l2h-948' class="method">compare</tt></b>(</nobr></td>
<td><var>a, b</var>)</td></tr></table></dt>
<dd>
Compare two sequences of lines, and generate the delta (a sequence
of lines).
<P>
Each sequence must contain individual single-line strings ending
with newlines. Such sequences can be obtained from the
<tt class="method">readlines()</tt> method of file-like objects. The delta generated
also consists of newline-terminated strings, ready to be printed as-is
via the <tt class="method">writelines()</tt> method of a file-like object.
</dl>
<P>
<DIV CLASS="navigation">
<div class='online-navigation'>
<p></p><hr />
<table align="center" width="100%" cellpadding="0" cellspacing="2">
<tr>
<td class='online-navigation'><a rel="prev" title="4.4.2 SequenceMatcher Examples"
href="sequencematcher-examples.html"><img src='../icons/previous.png'
border='0' height='32' alt='Previous Page' width='32' /></A></td>
<td class='online-navigation'><a rel="parent" title="4.4 difflib "
href="module-difflib.html"><img src='../icons/up.png'
border='0' height='32' alt='Up One Level' width='32' /></A></td>
<td class='online-navigation'><a rel="next" title="4.4.4 Differ Example"
href="differ-examples.html"><img src='../icons/next.png'
border='0' height='32' alt='Next Page' width='32' /></A></td>
<td align="center" width="100%">Python Library Reference</td>
<td class='online-navigation'><a rel="contents" title="Table of Contents"
href="contents.html"><img src='../icons/contents.png'
border='0' height='32' alt='Contents' width='32' /></A></td>
<td class='online-navigation'><a href="modindex.html" title="Module Index"><img src='../icons/modules.png'
border='0' height='32' alt='Module Index' width='32' /></a></td>
<td class='online-navigation'><a rel="index" title="Index"
href="genindex.html"><img src='../icons/index.png'
border='0' height='32' alt='Index' width='32' /></A></td>
</tr></table>
<div class='online-navigation'>
<b class="navlabel">Previous:</b>
<a class="sectref" rel="prev" href="sequencematcher-examples.html">4.4.2 SequenceMatcher Examples</A>
<b class="navlabel">Up:</b>
<a class="sectref" rel="parent" href="module-difflib.html">4.4 difflib </A>
<b class="navlabel">Next:</b>
<a class="sectref" rel="next" href="differ-examples.html">4.4.4 Differ Example</A>
</div>
</div>
<hr />
<span class="release-info">Release 2.4.3, documentation updated on 29 March 2006.</span>
</DIV>
<!--End of Navigation Panel-->
<ADDRESS>
See <i><a href="about.html">About this document...</a></i> for information on suggesting changes.
</ADDRESS>
</BODY>
</HTML>