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(python2.1-lib.info)Examples 2

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Prev: SequenceMatcher Objects Up: difflib

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Enter node , (file) or (file)node

Examples
--------

This example compares two strings, considering blanks to be "junk:"

     >>> s = SequenceMatcher(lambda x: x == " ",
     ...                     "private Thread currentThread;",
     ...                     "private volatile Thread currentThread;")

`ratio()' returns a float in [0, 1], measuring the similarity of the
sequences.  As a rule of thumb, a `ratio()' value over 0.6 means the
sequences are close matches:

     >>> print round(s.ratio(), 3)
     0.866

If you're only interested in where the sequences match,
`get_matching_blocks()' is handy:

     >>> 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 `get_matching_blocks()' is always
a dummy, `(len(A), len(B), 0)', and this is the only case in which the
last tuple element (number of elements matched) is `0'.

If you want to know how to change the first sequence into the second,
use `get_opcodes()':

     >>> for opcode in s.get_opcodes():
     ...     print "%6s a[%d:%d] b[%d:%d]" % opcode
      equal a[0:8] b[0:8]
     insert a[8:8] b[8:17]
      equal a[8:14] b[17:23]
      equal a[14:29] b[23:38]

See `Tools/scripts/ndiff.py' from the Python source distribution for a
fancy human-friendly file differencer, which uses `SequenceMatcher'
both to view files as sequences of lines, and lines as sequences of
characters.

See also the function `get_close_matches()' in this module, which shows
how simple code building on `SequenceMatcher' can be used to do useful
work.