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<title>4.4.2 SequenceMatcher Examples
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4.4.2 SequenceMatcher Examples
This example compares two strings, considering blanks to be ``junk:''
<div class=
"verbatim"><pre>
>>> s = SequenceMatcher(lambda x: x ==
" ",
...
"private Thread currentThread;",
...
"private volatile Thread currentThread;")
<tt class=
"method">ratio()
</tt> returns a float in [
0,
1], measuring the similarity
of the sequences. As a rule of thumb, a
<tt class=
"method">ratio()
</tt> value over
0.6 means the sequences are close matches:
<div class=
"verbatim"><pre>
>>> print round(s.ratio(),
3)
If you're only interested in where the sequences match,
<tt class=
"method">get_matching_blocks()
</tt> is handy:
<div class=
"verbatim"><pre>
>>> for block in s.get_matching_blocks():
... print
"a[%d] and b[%d] match for %d elements" % block
a[
0] and b[
0] match for
8 elements
a[
8] and b[
17] match for
6 elements
a[
14] and b[
23] match for
15 elements
a[
29] and b[
38] match for
0 elements
Note that the last tuple returned by
<tt class=
"method">get_matching_blocks()
</tt> is
always a dummy,
<code>(len(
<var>a
</var>), len(
<var>b
</var>),
0)
</code>, and this is
the only case in which the last tuple element (number of elements
matched) is
<code>0</code>.
If you want to know how to change the first sequence into the second,
use
<tt class=
"method">get_opcodes()
</tt>:
<div class=
"verbatim"><pre>
>>> for opcode in s.get_opcodes():
... print
"%6s a[%d:%d] b[%d:%d]" % opcode
See also the function
<tt class=
"function">get_close_matches()
</tt> in this module,
which shows how simple code building on
<tt class=
"class">SequenceMatcher
</tt> can be
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<span class=
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