cpython-lru_cache-weakref: Doc/lib/libdifflib.tex annotate

annotate Doc/lib/libdifflib.tex @ 17382:d368552c2b72 legacy-trunk

Add reference to the DDJ article discussing a similar algorithm.

author	Fred Drake <fdrake@acm.org>
date	Tue, 10 Apr 2001 18:41:16 +0000
parents	8996288a8873
children	e4abe74bc973

rev	line source
16682 3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	1 \section{\module{difflib} ---
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	2 Helpers for computing deltas}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	3
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	4 \declaremodule{standard}{difflib}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	5 \modulesynopsis{Helpers for computing differences between objects.}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	6 \moduleauthor{Tim Peters}{tim.one@home.com}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	7 \sectionauthor{Tim Peters}{tim.one@home.com}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	8 % LaTeXification by Fred L. Drake, Jr. <fdrake@acm.org>.
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	9
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	10 \begin{funcdesc}{get_close_matches}{word, possibilities\optional{,
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	11 n\optional{, cutoff}}}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	12 Return a list of the best ``good enough'' matches. \var{word} is a
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	13 sequence for which close matches are desired (typically a string),
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	14 and \var{possibilities} is a list of sequences against which to
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	15 match \var{word} (typically a list of strings).
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	16
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	17 Optional argument \var{n} (default \code{3}) is the maximum number
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	18 of close matches to return; \var{n} must be greater than \code{0}.
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	19
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	20 Optional argument \var{cutoff} (default \code{0.6}) is a float in
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	21 the range [0, 1]. Possibilities that don't score at least that
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	22 similar to \var{word} are ignored.
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	23
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	24 The best (no more than \var{n}) matches among the possibilities are
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	25 returned in a list, sorted by similarity score, most similar first.
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	26
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	27 \begin{verbatim}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	28 >>> get_close_matches('appel', ['ape', 'apple', 'peach', 'puppy'])
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	29 ['apple', 'ape']
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	30 >>> import keyword
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	31 >>> get_close_matches('wheel', keyword.kwlist)
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	32 ['while']
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	33 >>> get_close_matches('apple', keyword.kwlist)
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	34 []
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	35 >>> get_close_matches('accept', keyword.kwlist)
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	36 ['except']
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	37 \end{verbatim}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	38 \end{funcdesc}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	39
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	40 \begin{classdesc}{SequenceMatcher}{\unspecified}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	41 This is a flexible class for comparing pairs of sequences of any
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	42 type, so long as the sequence elements are hashable. The basic
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	43 algorithm predates, and is a little fancier than, an algorithm
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	44 published in the late 1980's by Ratcliff and Obershelp under the
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	45 hyperbolic name ``gestalt pattern matching.'' The idea is to find
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	46 the longest contiguous matching subsequence that contains no
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	47 ``junk'' elements (the Ratcliff and Obershelp algorithm doesn't
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	48 address junk). The same idea is then applied recursively to the
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	49 pieces of the sequences to the left and to the right of the matching
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	50 subsequence. This does not yield minimal edit sequences, but does
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	51 tend to yield matches that ``look right'' to people.
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	52
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	53 \strong{Timing:} The basic Ratcliff-Obershelp algorithm is cubic
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	54 time in the worst case and quadratic time in the expected case.
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	55 \class{SequenceMatcher} is quadratic time for the worst case and has
16703 8172906c6dc8 Improve accuracy. In the .tex file, note the new "% BUG:" comments: an Tim Peters <tim.peters@gmail.com> parents: 16682 diff changeset	56 expected-case behavior dependent in a complicated way on how many
8172906c6dc8 Improve accuracy. In the .tex file, note the new "% BUG:" comments: an Tim Peters <tim.peters@gmail.com> parents: 16682 diff changeset	57 elements the sequences have in common; best case time is linear.
16682 3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	58 \end{classdesc}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	59
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	60
17382 d368552c2b72 Add reference to the DDJ article discussing a similar algorithm. Fred Drake <fdrake@acm.org> parents: 16758 diff changeset	61 \begin{seealso}
d368552c2b72 Add reference to the DDJ article discussing a similar algorithm. Fred Drake <fdrake@acm.org> parents: 16758 diff changeset	62 \seetitle{Pattern Matching: The Gestalt Approach}{Discussion of a
d368552c2b72 Add reference to the DDJ article discussing a similar algorithm. Fred Drake <fdrake@acm.org> parents: 16758 diff changeset	63 similar algorithm by John W. Ratcliff and D. E. Metzener.
d368552c2b72 Add reference to the DDJ article discussing a similar algorithm. Fred Drake <fdrake@acm.org> parents: 16758 diff changeset	64 This was published in
d368552c2b72 Add reference to the DDJ article discussing a similar algorithm. Fred Drake <fdrake@acm.org> parents: 16758 diff changeset	65 \citetitle[http://www.ddj.com/]{Dr. Dobb's Journal} in
d368552c2b72 Add reference to the DDJ article discussing a similar algorithm. Fred Drake <fdrake@acm.org> parents: 16758 diff changeset	66 July, 1988.}
d368552c2b72 Add reference to the DDJ article discussing a similar algorithm. Fred Drake <fdrake@acm.org> parents: 16758 diff changeset	67 \end{seealso}
d368552c2b72 Add reference to the DDJ article discussing a similar algorithm. Fred Drake <fdrake@acm.org> parents: 16758 diff changeset	68
d368552c2b72 Add reference to the DDJ article discussing a similar algorithm. Fred Drake <fdrake@acm.org> parents: 16758 diff changeset	69
16682 3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	70 \subsection{SequenceMatcher Objects \label{sequence-matcher}}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	71
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	72 \begin{classdesc}{SequenceMatcher}{\optional{isjunk\optional{,
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	73 a\optional{, b}}}}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	74 Optional argument \var{isjunk} must be \code{None} (the default) or
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	75 a one-argument function that takes a sequence element and returns
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	76 true if and only if the element is ``junk'' and should be ignored.
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	77 \code{None} is equivalent to passing \code{lambda x: 0}, i.e.\ no
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	78 elements are ignored. For example, pass
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	79
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	80 \begin{verbatim}
16758 8996288a8873 Fix extra backslash in example. Fred Drake <fdrake@acm.org> parents: 16703 diff changeset	81 lambda x: x in " \t"
16682 3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	82 \end{verbatim}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	83
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	84 if you're comparing lines as sequences of characters, and don't want
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	85 to synch up on blanks or hard tabs.
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	86
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	87 The optional arguments \var{a} and \var{b} are sequences to be
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	88 compared; both default to empty strings. The elements of both
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	89 sequences must be hashable.
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	90 \end{classdesc}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	91
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	92
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	93 \class{SequenceMatcher} objects have the following methods:
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	94
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	95 \begin{methoddesc}{set_seqs}{a, b}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	96 Set the two sequences to be compared.
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	97 \end{methoddesc}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	98
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	99 \class{SequenceMatcher} computes and caches detailed information about
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	100 the second sequence, so if you want to compare one sequence against
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	101 many sequences, use \method{set_seq2()} to set the commonly used
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	102 sequence once and call \method{set_seq1()} repeatedly, once for each
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	103 of the other sequences.
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	104
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	105 \begin{methoddesc}{set_seq1}{a}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	106 Set the first sequence to be compared. The second sequence to be
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	107 compared is not changed.
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	108 \end{methoddesc}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	109
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	110 \begin{methoddesc}{set_seq2}{b}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	111 Set the second sequence to be compared. The first sequence to be
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	112 compared is not changed.
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	113 \end{methoddesc}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	114
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	115 \begin{methoddesc}{find_longest_match}{alo, ahi, blo, bhi}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	116 Find longest matching block in \code{\var{a}[\var{alo}:\var{ahi}]}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	117 and \code{\var{b}[\var{blo}:\var{bhi}]}.
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	118
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	119 If \var{isjunk} was omitted or \code{None},
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	120 \method{get_longest_match()} returns \code{(\var{i}, \var{j},
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	121 \var{k})} such that \code{\var{a}[\var{i}:\var{i}+\var{k}]} is equal
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	122 to \code{\var{b}[\var{j}:\var{j}+\var{k}]}, where
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	123 \code{\var{alo} <= \var{i} <= \var{i}+\var{k} <= \var{ahi}} and
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	124 \code{\var{blo} <= \var{j} <= \var{j}+\var{k} <= \var{bhi}}.
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	125 For all \code{(\var{i'}, \var{j'}, \var{k'})} meeting those
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	126 conditions, the additional conditions
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	127 \code{\var{k} >= \var{k'}},
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	128 \code{\var{i} <= \var{i'}},
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	129 and if \code{\var{i} == \var{i'}}, \code{\var{j} <= \var{j'}}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	130 are also met.
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	131 In other words, of all maximal matching blocks, return one that
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	132 starts earliest in \var{a}, and of all those maximal matching blocks
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	133 that start earliest in \var{a}, return the one that starts earliest
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	134 in \var{b}.
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	135
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	136 \begin{verbatim}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	137 >>> s = SequenceMatcher(None, " abcd", "abcd abcd")
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	138 >>> s.find_longest_match(0, 5, 0, 9)
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	139 (0, 4, 5)
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	140 \end{verbatim}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	141
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	142 If \var{isjunk} was provided, first the longest matching block is
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	143 determined as above, but with the additional restriction that no
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	144 junk element appears in the block. Then that block is extended as
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	145 far as possible by matching (only) junk elements on both sides.
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	146 So the resulting block never matches on junk except as identical
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	147 junk happens to be adjacent to an interesting match.
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	148
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	149 Here's the same example as before, but considering blanks to be junk.
16703 8172906c6dc8 Improve accuracy. In the .tex file, note the new "% BUG:" comments: an Tim Peters <tim.peters@gmail.com> parents: 16682 diff changeset	150 That prevents \code{' abcd'} from matching the \code{' abcd'} at the
16682 3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	151 tail end of the second sequence directly. Instead only the
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	152 \code{'abcd'} can match, and matches the leftmost \code{'abcd'} in
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	153 the second sequence:
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	154
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	155 \begin{verbatim}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	156 >>> s = SequenceMatcher(lambda x: x==" ", " abcd", "abcd abcd")
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	157 >>> s.find_longest_match(0, 5, 0, 9)
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	158 (1, 0, 4)
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	159 \end{verbatim}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	160
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	161 If no blocks match, this returns \code{(\var{alo}, \var{blo}, 0)}.
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	162 \end{methoddesc}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	163
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	164 \begin{methoddesc}{get_matching_blocks}{}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	165 Return list of triples describing matching subsequences.
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	166 Each triple is of the form \code{(\var{i}, \var{j}, \var{n})}, and
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	167 means that \code{\var{a}[\var{i}:\var{i}+\var{n}] ==
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	168 \var{b}[\var{j}:\var{j}+\var{n}]}. The triples are monotonically
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	169 increasing in \var{i} and \var{j}.
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	170
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	171 The last triple is a dummy, and has the value \code{(len(\var{a}),
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	172 len(\var{b}), 0)}. It is the only triple with \code{\var{n} == 0}.
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	173 % Explain why a dummy is used!
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	174
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	175 \begin{verbatim}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	176 >>> s = SequenceMatcher(None, "abxcd", "abcd")
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	177 >>> s.get_matching_blocks()
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	178 [(0, 0, 2), (3, 2, 2), (5, 4, 0)]
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	179 \end{verbatim}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	180 \end{methoddesc}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	181
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	182 \begin{methoddesc}{get_opcodes}{}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	183 Return list of 5-tuples describing how to turn \var{a} into \var{b}.
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	184 Each tuple is of the form \code{(\var{tag}, \var{i1}, \var{i2},
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	185 \var{j1}, \var{j2})}. The first tuple has \code{\var{i1} ==
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	186 \var{j1} == 0}, and remaining tuples have \var{i1} equal to the
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	187 \var{i2} from the preceeding tuple, and, likewise, \var{j1} equal to
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	188 the previous \var{j2}.
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	189
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	190 The \var{tag} values are strings, with these meanings:
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	191
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	192 \begin{tableii}{l\|l}{code}{Value}{Meaning}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	193 \lineii{'replace'}{\code{\var{a}[\var{i1}:\var{i2}]} should be
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	194 replaced by \code{\var{b}[\var{j1}:\var{j2}]}.}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	195 \lineii{'delete'}{\code{\var{a}[\var{i1}:\var{i2}]} should be
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	196 deleted. Note that \code{\var{j1} == \var{j2}} in
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	197 this case.}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	198 \lineii{'insert'}{\code{\var{b}[\var{j1}:\var{j2}]} should be
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	199 inserted at \code{\var{a}[\var{i1}:\var{i1}]}.
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	200 Note that \code{\var{i1} == \var{i2}} in this
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	201 case.}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	202 \lineii{'equal'}{\code{\var{a}[\var{i1}:\var{i2}] ==
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	203 \var{b}[\var{j1}:\var{j2}]} (the sub-sequences are
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	204 equal).}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	205 \end{tableii}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	206
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	207 For example:
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	208
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	209 \begin{verbatim}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	210 >>> a = "qabxcd"
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	211 >>> b = "abycdf"
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	212 >>> s = SequenceMatcher(None, a, b)
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	213 >>> for tag, i1, i2, j1, j2 in s.get_opcodes():
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	214 ... print ("%7s a[%d:%d] (%s) b[%d:%d] (%s)" %
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	215 ... (tag, i1, i2, a[i1:i2], j1, j2, b[j1:j2]))
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	216 delete a[0:1] (q) b[0:0] ()
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	217 equal a[1:3] (ab) b[0:2] (ab)
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	218 replace a[3:4] (x) b[2:3] (y)
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	219 equal a[4:6] (cd) b[3:5] (cd)
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	220 insert a[6:6] () b[5:6] (f)
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	221 \end{verbatim}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	222 \end{methoddesc}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	223
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	224 \begin{methoddesc}{ratio}{}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	225 Return a measure of the sequences' similarity as a float in the
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	226 range [0, 1].
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	227
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	228 Where T is the total number of elements in both sequences, and M is
16703 8172906c6dc8 Improve accuracy. In the .tex file, note the new "% BUG:" comments: an Tim Peters <tim.peters@gmail.com> parents: 16682 diff changeset	229 the number of matches, this is 2.0*M / T. Note that this is \code{1.}
8172906c6dc8 Improve accuracy. In the .tex file, note the new "% BUG:" comments: an Tim Peters <tim.peters@gmail.com> parents: 16682 diff changeset	230 if the sequences are identical, and \code{0.} if they have nothing in
16682 3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	231 common.
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	232
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	233 This is expensive to compute if \method{get_matching_blocks()} or
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	234 \method{get_opcodes()} hasn't already been called, in which case you
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	235 may want to try \method{quick_ratio()} or
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	236 \method{real_quick_ratio()} first to get an upper bound.
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	237 \end{methoddesc}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	238
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	239 \begin{methoddesc}{quick_ratio}{}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	240 Return an upper bound on \method{ratio()} relatively quickly.
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	241
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	242 This isn't defined beyond that it is an upper bound on
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	243 \method{ratio()}, and is faster to compute.
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	244 \end{methoddesc}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	245
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	246 \begin{methoddesc}{real_quick_ratio}{}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	247 Return an upper bound on \method{ratio()} very quickly.
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	248
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	249 This isn't defined beyond that it is an upper bound on
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	250 \method{ratio()}, and is faster to compute than either
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	251 \method{ratio()} or \method{quick_ratio()}.
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	252 \end{methoddesc}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	253
16703 8172906c6dc8 Improve accuracy. In the .tex file, note the new "% BUG:" comments: an Tim Peters <tim.peters@gmail.com> parents: 16682 diff changeset	254 The three methods that return the ratio of matching to total characters
8172906c6dc8 Improve accuracy. In the .tex file, note the new "% BUG:" comments: an Tim Peters <tim.peters@gmail.com> parents: 16682 diff changeset	255 can give different results due to differing levels of approximation,
8172906c6dc8 Improve accuracy. In the .tex file, note the new "% BUG:" comments: an Tim Peters <tim.peters@gmail.com> parents: 16682 diff changeset	256 although \method{quick_ratio()} and \method{real_quick_ratio()} are always
8172906c6dc8 Improve accuracy. In the .tex file, note the new "% BUG:" comments: an Tim Peters <tim.peters@gmail.com> parents: 16682 diff changeset	257 at least as large as \method{ratio()}:
16682 3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	258
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	259 \begin{verbatim}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	260 >>> s = SequenceMatcher(None, "abcd", "bcde")
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	261 >>> s.ratio()
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	262 0.75
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	263 >>> s.quick_ratio()
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	264 0.75
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	265 >>> s.real_quick_ratio()
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	266 1.0
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	267 \end{verbatim}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	268
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	269
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	270 \subsection{Examples \label{difflib-examples}}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	271
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	272
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	273 This example compares two strings, considering blanks to be ``junk:''
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	274
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	275 \begin{verbatim}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	276 >>> s = SequenceMatcher(lambda x: x == " ",
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	277 ... "private Thread currentThread;",
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	278 ... "private volatile Thread currentThread;")
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	279 \end{verbatim}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	280
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	281 \method{ratio()} returns a float in [0, 1], measuring the similarity
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	282 of the sequences. As a rule of thumb, a \method{ratio()} value over
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	283 0.6 means the sequences are close matches:
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	284
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	285 \begin{verbatim}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	286 >>> print round(s.ratio(), 3)
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	287 0.866
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	288 \end{verbatim}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	289
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	290 If you're only interested in where the sequences match,
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	291 \method{get_matching_blocks()} is handy:
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	292
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	293 \begin{verbatim}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	294 >>> for block in s.get_matching_blocks():
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	295 ... print "a[%d] and b[%d] match for %d elements" % block
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	296 a[0] and b[0] match for 8 elements
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	297 a[8] and b[17] match for 6 elements
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	298 a[14] and b[23] match for 15 elements
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	299 a[29] and b[38] match for 0 elements
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	300 \end{verbatim}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	301
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	302 Note that the last tuple returned by \method{get_matching_blocks()} is
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	303 always a dummy, \code{(len(\var{a}), len(\var{b}), 0)}, and this is
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	304 the only case in which the last tuple element (number of elements
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	305 matched) is \code{0}.
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	306
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	307 If you want to know how to change the first sequence into the second,
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	308 use \method{get_opcodes()}:
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	309
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	310 \begin{verbatim}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	311 >>> for opcode in s.get_opcodes():
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	312 ... print "%6s a[%d:%d] b[%d:%d]" % opcode
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	313 equal a[0:8] b[0:8]
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	314 insert a[8:8] b[8:17]
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	315 equal a[8:14] b[17:23]
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	316 equal a[14:29] b[23:38]
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	317 \end{verbatim}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	318
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	319 See \file{Tools/scripts/ndiff.py} from the Python source distribution
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	320 for a fancy human-friendly file differencer, which uses
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	321 \class{SequenceMatcher} both to view files as sequences of lines, and
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	322 lines as sequences of characters.
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	323
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	324 See also the function \function{get_close_matches()} in this module,
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	325 which shows how simple code building on \class{SequenceMatcher} can be
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	326 used to do useful work.

Mercurial > cpython-lru_cache-weakref

annotate Doc/lib/libdifflib.tex @ 17382:d368552c2b72 legacy-trunk