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<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>&nbsp;<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>

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Commit	Line	Data
86530b38 AT	1	<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
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	54
	55	<H2><A NAME="SECTION006430000000000000000"></A><A NAME="differ-objects"></A>
	56	<BR>
	57	4.4.3 Differ Objects
	58	</H2>
	59
	60	<P>
	61	Note that <tt class="class">Differ</tt>-generated deltas make no claim to be
	62	<strong>minimal</strong> diffs. To the contrary, minimal diffs are often
	63	counter-intuitive, because they synch up anywhere possible, sometimes
	64	accidental matches 100 pages apart. Restricting synch points to
65	contiguous matches preserves some notion of locality, at the
66	occasional cost of producing a longer diff.
67
68	<P>
69	The <tt class="class">Differ</tt> class has this constructor:
70
71	<P>
72	<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
73	<td><nobr><b><span class="typelabel">class</span> <tt id='l2h-947' xml:id='l2h-947' class="class">Differ</tt></b>(</nobr></td>
74	<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>
75	<dd>
76	Optional keyword parameters <var>linejunk</var> and <var>charjunk</var> are
77	for filter functions (or <code>None</code>):
78
79	<P>
80	<var>linejunk</var>: A function that accepts a single string
81	argument, and returns true if the string is junk. The default is
82	<code>None</code>, meaning that no line is considered junk.
83
84	<P>
85	<var>charjunk</var>: A function that accepts a single character argument
86	(a string of length 1), and returns true if the character is junk.
87	The default is <code>None</code>, meaning that no character is
88	considered junk.
89	</dl>
90
91	<P>
92	<tt class="class">Differ</tt> objects are used (deltas generated) via a single
93	method:
94
95	<P>
96	<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
97	<td><nobr><b><tt id='l2h-948' xml:id='l2h-948' class="method">compare</tt></b>(</nobr></td>
98	<td><var>a, b</var>)</td></tr></table></dt>
99	<dd>
100	Compare two sequences of lines, and generate the delta (a sequence
101	of lines).
102
103	<P>
104	Each sequence must contain individual single-line strings ending
105	with newlines. Such sequences can be obtained from the
106	<tt class="method">readlines()</tt> method of file-like objects. The delta generated
107	also consists of newline-terminated strings, ready to be printed as-is
108	via the <tt class="method">writelines()</tt> method of a file-like object.
109	</dl>
110
111	<P>
112
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