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Python Library Reference |  |
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Python Library Reference | |
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New in version 2.1.
Timing: The basic Ratcliff-Obershelp algorithm is cubic time in the worst case and quadratic time in the expected case. SequenceMatcher is quadratic time for the worst case and has expected-case behavior dependent in a complicated way on how many elements the sequences have in common; best case time is linear.
Each line of a Differ delta begins with a two-letter code:
| Code | Meaning |
|---|---|
'- ' |
line unique to sequence 1 |
'+ ' |
line unique to sequence 2 |
' ' |
line common to both sequences |
'? ' |
line not present in either input sequence |
Lines beginning with `? ' attempt to guide the eye to
intraline differences, and were not present in either input
sequence. These lines can be confusing if the sequences contain tab
characters.
| a, b[, fromfile[, tofile [, fromfiledate[, tofiledate[, n [, lineterm]]]]]]) |
Compare a and b (lists of strings); return a delta (a generator generating the delta lines) in context diff format.
Context diffs are a compact way of showing just the lines that have changed plus a few lines of context. The changes are shown in a before/after style. The number of context lines is set by n which defaults to three.
By default, the diff control lines (those with *** or --)
are created with a trailing newline. This is helpful so that inputs created
from file.readlines() result in diffs that are suitable for use
with file.writelines() since both the inputs and outputs have
trailing newlines.
For inputs that do not have trailing newlines, set the lineterm
argument to "" so that the output will be uniformly newline free.
The context diff format normally has a header for filenames and modification times. Any or all of these may be specified using strings for fromfile, tofile, fromfiledate, and tofiledate. The modification times are normally expressed in the format returned by time.ctime(). If not specified, the strings default to blanks.
Tools/scripts/diff.py is a command-line front-end for this function.
New in version 2.3.
| word, possibilities[, n[, cutoff]]) |
Optional argument n (default 3) is the maximum number
of close matches to return; n must be greater than 0.
Optional argument cutoff (default 0.6) is a float in
the range [0, 1]. Possibilities that don't score at least that
similar to word are ignored.
The best (no more than n) matches among the possibilities are returned in a list, sorted by similarity score, most similar first.
>>> get_close_matches('appel', ['ape', 'apple', 'peach', 'puppy'])
['apple', 'ape']
>>> import keyword
>>> get_close_matches('wheel', keyword.kwlist)
['while']
>>> get_close_matches('apple', keyword.kwlist)
[]
>>> get_close_matches('accept', keyword.kwlist)
['except']
| a, b[, linejunk[, charjunk]]) |
Optional keyword parameters linejunk and charjunk are
for filter functions (or None):
linejunk: A function that accepts a single string
argument, and returns true if the string is junk, or false if not.
The default is (None), starting with Python 2.3. Before then,
the default was the module-level function
IS_LINE_JUNK(), which filters out lines without visible
characters, except for at most one pound character ("#").
As of Python 2.3, the underlying SequenceMatcher class
does a dynamic analysis of which lines are so frequent as to
constitute noise, and this usually works better than the pre-2.3
default.
charjunk: A function that accepts a character (a string of length 1), and returns if the character is junk, or false if not. The default is module-level function IS_CHARACTER_JUNK(), which filters out whitespace characters (a blank or tab; note: bad idea to include newline in this!).
Tools/scripts/ndiff.py is a command-line front-end to this function.
>>> diff = ndiff('one\ntwo\nthree\n'.splitlines(1),
... 'ore\ntree\nemu\n'.splitlines(1))
>>> print ''.join(diff),
- one
? ^
+ ore
? ^
- two
- three
? -
+ tree
+ emu
| sequence, which) |
Given a sequence produced by Differ.compare() or ndiff(), extract lines originating from file 1 or 2 (parameter which), stripping off line prefixes.
Example:
>>> diff = ndiff('one\ntwo\nthree\n'.splitlines(1),
... 'ore\ntree\nemu\n'.splitlines(1))
>>> diff = list(diff) # materialize the generated delta into a list
>>> print ''.join(restore(diff, 1)),
one
two
three
>>> print ''.join(restore(diff, 2)),
ore
tree
emu
| a, b[, fromfile[, tofile [, fromfiledate[, tofiledate[, n [, lineterm]]]]]]) |
Compare a and b (lists of strings); return a delta (a generator generating the delta lines) in unified diff format.
Unified diffs are a compact way of showing just the lines that have changed plus a few lines of context. The changes are shown in a inline style (instead of separate before/after blocks). The number of context lines is set by n which defaults to three.
By default, the diff control lines (those with --, +++,
or @@) are created with a trailing newline. This is helpful so
that inputs created from file.readlines() result in diffs
that are suitable for use with file.writelines() since both
the inputs and outputs have trailing newlines.
For inputs that do not have trailing newlines, set the lineterm
argument to "" so that the output will be uniformly newline free.
The context diff format normally has a header for filenames and modification times. Any or all of these may be specified using strings for fromfile, tofile, fromfiledate, and tofiledate. The modification times are normally expressed in the format returned by time.ctime(). If not specified, the strings default to blanks.
Tools/scripts/diff.py is a command-line front-end for this function.
New in version 2.3.
| line) |
| ch) |
See Also:
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Python Library Reference | |
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