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

annotate Doc/lib/libdifflib.tex @ 19232:65885ea76c37 legacy-trunk

David Goodger <dgoodger@atsautomation.com>: Documentation for difflib/ndiff refactoring: more of the ndiff functionality has been moved to the underlying library (difflib). This closes SF patch #445413.

author	Fred Drake <fdrake@acm.org>
date	Mon, 13 Aug 2001 19:31:59 +0000
parents	0ed8c5f3f530
children	8a6f2ee6eaba

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
17388 e4abe74bc973 Add note that difflib was added in Python 2.1. Fred Drake <fdrake@acm.org> parents: 17382 diff changeset	10 \versionadded{2.1}
e4abe74bc973 Add note that difflib was added in Python 2.1. Fred Drake <fdrake@acm.org> parents: 17382 diff changeset	11
e4abe74bc973 Add note that difflib was added in Python 2.1. Fred Drake <fdrake@acm.org> parents: 17382 diff changeset	12
19232 65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	13 \begin{classdesc*}{SequenceMatcher}
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	14 This is a flexible class for comparing pairs of sequences of any
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	15 type, so long as the sequence elements are hashable. The basic
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	16 algorithm predates, and is a little fancier than, an algorithm
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	17 published in the late 1980's by Ratcliff and Obershelp under the
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	18 hyperbolic name ``gestalt pattern matching.'' The idea is to find
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	19 the longest contiguous matching subsequence that contains no
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	20 ``junk'' elements (the Ratcliff and Obershelp algorithm doesn't
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	21 address junk). The same idea is then applied recursively to the
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	22 pieces of the sequences to the left and to the right of the matching
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	23 subsequence. This does not yield minimal edit sequences, but does
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	24 tend to yield matches that ``look right'' to people.
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	25
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	26 \strong{Timing:} The basic Ratcliff-Obershelp algorithm is cubic
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	27 time in the worst case and quadratic time in the expected case.
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	28 \class{SequenceMatcher} is quadratic time for the worst case and has
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	29 expected-case behavior dependent in a complicated way on how many
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	30 elements the sequences have in common; best case time is linear.
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	31 \end{classdesc*}
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	32
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	33 \begin{classdesc*}{Differ}
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	34 This is a class for comparing sequences of lines of text, and
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	35 producing human-readable differences or deltas. Differ uses
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	36 \class{SequenceMatcher} both to compare sequences of lines, and to
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	37 compare sequences of characters within similar (near-matching)
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	38 lines.
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	39
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	40 Each line of a \class{Differ} delta begins with a two-letter code:
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	41
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	42 \begin{tableii}{l\|l}{code}{Code}{Meaning}
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	43 \lineii{'- '}{line unique to sequence 1}
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	44 \lineii{'+ '}{line unique to sequence 2}
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	45 \lineii{' '}{line common to both sequences}
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	46 \lineii{'? '}{line not present in either input sequence}
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	47 \end{tableii}
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	48
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	49 Lines beginning with `\code{?~}' attempt to guide the eye to
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	50 intraline differences, and were not present in either input
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	51 sequence. These lines can be confusing if the sequences contain tab
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	52 characters.
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	53 \end{classdesc*}
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	54
16682 3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	55 \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	56 n\optional{, cutoff}}}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	57 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	58 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	59 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	60 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	61
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	62 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	63 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	64
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	65 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	66 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	67 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	68
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	69 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	70 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	71
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	72 \begin{verbatim}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	73 >>> 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	74 ['apple', 'ape']
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	75 >>> import keyword
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	76 >>> 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	77 ['while']
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	78 >>> 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	79 []
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	80 >>> 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	81 ['except']
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 \end{funcdesc}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	84
19232 65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	85 \begin{funcdesc}{ndiff}{a, b\optional{, linejunk\optional{,
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	86 charjunk}}}
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	87 Compare \var{a} and \var{b} (lists of strings); return a
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	88 \class{Differ}-style delta.
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	89
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	90 Optional keyword parameters \var{linejunk} and \var{charjunk} are
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	91 for filter functions (or \code{None}):
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	92
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	93 \var{linejunk}: A function that should accept a single string
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	94 argument, and return true if the string is junk (or false if it is
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	95 not). The default is module-level function
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	96 \function{IS_LINE_JUNK()}, which filters out lines without visible
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	97 characters, except for at most one pound character (\character{\#}).
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	98
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	99 \var{charjunk}: A function that should accept a string of length 1.
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	100 The default is module-level function \function{IS_CHARACTER_JUNK()},
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	101 which filters out whitespace characters (a blank or tab; note: bad
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	102 idea to include newline in this!).
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	103
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	104 \file{Tools/scripts/ndiff.py} is a command-line front-end to this
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	105 function.
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	106
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	107 \begin{verbatim}
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	108 >>> diff = ndiff('one\ntwo\nthree\n'.splitlines(1),
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	109 ... 'ore\ntree\nemu\n'.splitlines(1)))
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	110 >>> print ''.join(diff),
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	111 - one
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	112 ? ^
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	113 + ore
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	114 ? ^
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	115 - two
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	116 - three
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	117 ? -
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	118 + tree
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	119 + emu
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	120 \end{verbatim}
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	121 \end{funcdesc}
16682 3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	122
19232 65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	123 \begin{funcdesc}{restore}{sequence, which}
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	124 Return one of the two sequences that generated a delta.
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	125
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	126 Given a \var{sequence} produced by \method{Differ.compare()} or
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	127 \function{ndiff()}, extract lines originating from file 1 or 2
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	128 (parameter \var{which}), stripping off line prefixes.
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	129
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	130 Example:
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	131
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	132 \begin{verbatim}
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	133 >>> diff = ndiff('one\ntwo\nthree\n'.splitlines(1),
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	134 ... 'ore\ntree\nemu\n'.splitlines(1))
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	135 >>> print ''.join(restore(diff, 1)),
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	136 one
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	137 two
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	138 three
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	139 >>> print ''.join(restore(diff, 2)),
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	140 ore
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	141 tree
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	142 emu
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	143 \end{verbatim}
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	144
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	145 \end{funcdesc}
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	146
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	147
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	148 \begin{funcdesc}{IS_LINE_JUNK}{line}:
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	149
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	150 Return 1 for ignorable line: iff \var{line} is blank or contains a
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	151 single \character{\#}. Used as a default for parameter
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	152 \var{linejunk} in \function{ndiff()}.
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	153
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	154 \end{funcdesc}
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	155
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	156
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	157 \begin{funcdesc}{IS_CHARACTER_JUNK}{ch}:
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	158
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	159 Return 1 for ignorable character: iff \var{ch} is a space or tab.
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	160 Used as a default for parameter \var{charjunk} in
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	161 \function{ndiff()}.
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	162
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	163 \end{funcdesc}
16682 3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	164
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	165
17382 d368552c2b72 Add reference to the DDJ article discussing a similar algorithm. Fred Drake <fdrake@acm.org> parents: 16758 diff changeset	166 \begin{seealso}
d368552c2b72 Add reference to the DDJ article discussing a similar algorithm. Fred Drake <fdrake@acm.org> parents: 16758 diff changeset	167 \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	168 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	169 This was published in
d368552c2b72 Add reference to the DDJ article discussing a similar algorithm. Fred Drake <fdrake@acm.org> parents: 16758 diff changeset	170 \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	171 July, 1988.}
d368552c2b72 Add reference to the DDJ article discussing a similar algorithm. Fred Drake <fdrake@acm.org> parents: 16758 diff changeset	172 \end{seealso}
d368552c2b72 Add reference to the DDJ article discussing a similar algorithm. Fred Drake <fdrake@acm.org> parents: 16758 diff changeset	173
d368552c2b72 Add reference to the DDJ article discussing a similar algorithm. Fred Drake <fdrake@acm.org> parents: 16758 diff changeset	174
16682 3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	175 \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	176
17780 a1575dbf7d81 Replace "\begin{classdesc}{SomeClass}{\unspecified}" with Fred Drake <fdrake@acm.org> parents: 17388 diff changeset	177 The \class{SequenceMatcher} class has this constructor:
a1575dbf7d81 Replace "\begin{classdesc}{SomeClass}{\unspecified}" with Fred Drake <fdrake@acm.org> parents: 17388 diff changeset	178
16682 3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	179 \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	180 a\optional{, b}}}}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	181 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	182 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	183 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	184 \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	185 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	186
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	187 \begin{verbatim}
16758 8996288a8873 Fix extra backslash in example. Fred Drake <fdrake@acm.org> parents: 16703 diff changeset	188 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	189 \end{verbatim}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	190
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	191 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	192 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	193
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	194 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	195 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	196 sequences must be hashable.
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	197 \end{classdesc}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	198
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	199
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	200 \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	201
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	202 \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	203 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	204 \end{methoddesc}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	205
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	206 \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	207 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	208 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	209 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	210 of the other sequences.
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	211
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	212 \begin{methoddesc}{set_seq1}{a}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	213 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	214 compared is not changed.
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	215 \end{methoddesc}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	216
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	217 \begin{methoddesc}{set_seq2}{b}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	218 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	219 compared is not changed.
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	220 \end{methoddesc}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	221
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	222 \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	223 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	224 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	225
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	226 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	227 \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	228 \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	229 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	230 \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	231 \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	232 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	233 conditions, the additional conditions
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	234 \code{\var{k} >= \var{k'}},
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	235 \code{\var{i} <= \var{i'}},
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	236 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	237 are also met.
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	238 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	239 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	240 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	241 in \var{b}.
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	242
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	243 \begin{verbatim}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	244 >>> 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	245 >>> 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	246 (0, 4, 5)
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	247 \end{verbatim}
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 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	250 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	251 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	252 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	253 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	254 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	255
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	256 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	257 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	258 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	259 \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	260 the second sequence:
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	261
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	262 \begin{verbatim}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	263 >>> 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	264 >>> 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	265 (1, 0, 4)
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	266 \end{verbatim}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	267
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	268 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	269 \end{methoddesc}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	270
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	271 \begin{methoddesc}{get_matching_blocks}{}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	272 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	273 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	274 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	275 \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	276 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	277
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	278 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	279 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	280 % 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	281
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	282 \begin{verbatim}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	283 >>> s = SequenceMatcher(None, "abxcd", "abcd")
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	284 >>> s.get_matching_blocks()
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	285 [(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	286 \end{verbatim}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	287 \end{methoddesc}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	288
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	289 \begin{methoddesc}{get_opcodes}{}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	290 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	291 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	292 \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	293 \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	294 \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	295 the previous \var{j2}.
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	296
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	297 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	298
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	299 \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	300 \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	301 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	302 \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	303 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	304 this case.}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	305 \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	306 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	307 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	308 case.}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	309 \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	310 \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	311 equal).}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	312 \end{tableii}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	313
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	314 For example:
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	315
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	316 \begin{verbatim}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	317 >>> a = "qabxcd"
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	318 >>> b = "abycdf"
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	319 >>> s = SequenceMatcher(None, a, b)
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	320 >>> 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	321 ... 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	322 ... (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	323 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	324 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	325 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	326 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	327 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	328 \end{verbatim}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	329 \end{methoddesc}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	330
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	331 \begin{methoddesc}{ratio}{}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	332 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	333 range [0, 1].
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	334
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	335 Where T is the total number of elements in both sequences, and M is
19232 65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	336 the number of matches, this is 2.0*M / T. Note that this is
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	337 \code{1.0} if the sequences are identical, and \code{0.0} if they
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	338 have nothing in common.
16682 3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	339
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	340 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	341 \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	342 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	343 \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	344 \end{methoddesc}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	345
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	346 \begin{methoddesc}{quick_ratio}{}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	347 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	348
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	349 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	350 \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	351 \end{methoddesc}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	352
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	353 \begin{methoddesc}{real_quick_ratio}{}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	354 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	355
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	356 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	357 \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	358 \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	359 \end{methoddesc}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	360
16703 8172906c6dc8 Improve accuracy. In the .tex file, note the new "% BUG:" comments: an Tim Peters <tim.peters@gmail.com> parents: 16682 diff changeset	361 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	362 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	363 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	364 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	365
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	366 \begin{verbatim}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	367 >>> s = SequenceMatcher(None, "abcd", "bcde")
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	368 >>> s.ratio()
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	369 0.75
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	370 >>> s.quick_ratio()
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	371 0.75
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	372 >>> s.real_quick_ratio()
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	373 1.0
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	374 \end{verbatim}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	375
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	376
19232 65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	377 \subsection{SequenceMatcher Examples \label{sequencematcher-examples}}
16682 3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	378
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	379
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	380 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	381
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	382 \begin{verbatim}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	383 >>> s = SequenceMatcher(lambda x: x == " ",
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	384 ... "private Thread currentThread;",
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	385 ... "private volatile Thread currentThread;")
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	386 \end{verbatim}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	387
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	388 \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	389 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	390 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	391
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	392 \begin{verbatim}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	393 >>> print round(s.ratio(), 3)
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	394 0.866
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	395 \end{verbatim}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	396
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	397 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	398 \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	399
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	400 \begin{verbatim}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	401 >>> 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	402 ... 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	403 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	404 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	405 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	406 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	407 \end{verbatim}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	408
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	409 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	410 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	411 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	412 matched) is \code{0}.
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	413
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	414 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	415 use \method{get_opcodes()}:
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	416
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	417 \begin{verbatim}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	418 >>> 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	419 ... 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	420 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	421 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	422 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	423 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	424 \end{verbatim}
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	425
3cb00cbe7455 Documentation for the difflib module, converted from the module docstrings. Fred Drake <fdrake@acm.org> parents: diff changeset	426 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	427 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	428 used to do useful work.
19232 65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	429
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	430
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	431 \subsection{Differ Objects \label{differ-objects}}
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	432
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	433 Note that \class{Differ}-generated deltas make no claim to be
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	434 \strong{minimal} diffs. To the contrary, minimal diffs are often
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	435 counter-intuitive, because they synch up anywhere possible, sometimes
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	436 accidental matches 100 pages apart. Restricting synch points to
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	437 contiguous matches preserves some notion of locality, at the
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	438 occasional cost of producing a longer diff.
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	439
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	440 The \class{Differ} class has this constructor:
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	441
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	442 \begin{classdesc}{Differ}{\optional{linejunk\optional{, charjunk}}}
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	443 Optional keyword parameters \var{linejunk} and \var{charjunk} are
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	444 for filter functions (or \code{None}):
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	445
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	446 \var{linejunk}: A function that should accept a single string
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	447 argument, and return true iff the string is junk. The default is
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	448 module-level function \function{IS_LINE_JUNK()}, which filters out
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	449 lines without visible characters, except for at most one pound
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	450 character (\character{\#}).
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	451
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	452 \var{charjunk}: A function that should accept a string of length 1.
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	453 The default is module-level function \function{IS_CHARACTER_JUNK()},
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	454 which filters out whitespace characters (a blank or tab; note: bad
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	455 idea to include newline in this!).
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	456 \end{classdesc}
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	457
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	458 \class{Differ} objects are used (deltas generated) via a single
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	459 method:
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	460
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	461 \begin{methoddesc}{compare}{a, b}
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	462 Compare two sequences of lines; return the resulting delta (list).
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	463
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	464 Each sequence must contain individual single-line strings ending
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	465 with newlines. Such sequences can be obtained from the
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	466 \method{readlines()} method of file-like objects. The list returned
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	467 is also made up of newline-terminated strings, and ready to be used
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	468 with the \method{writelines()} method of a file-like object.
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	469 \end{methoddesc}
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	470
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	471
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	472 \subsection{Differ Example \label{differ-examples}}
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	473
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	474 This example compares two texts. First we set up the texts, sequences
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	475 of individual single-line strings ending with newlines (such sequences
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	476 can also be obtained from the \method{readlines()} method of file-like
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	477 objects):
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	478
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	479 \begin{verbatim}
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	480 >>> text1 = ''' 1. Beautiful is better than ugly.
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	481 ... 2. Explicit is better than implicit.
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	482 ... 3. Simple is better than complex.
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	483 ... 4. Complex is better than complicated.
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	484 ... '''.splitlines(1)
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	485 >>> len(text1)
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	486 4
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	487 >>> text1[0][-1]
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	488 '\n'
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	489 >>> text2 = ''' 1. Beautiful is better than ugly.
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	490 ... 3. Simple is better than complex.
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	491 ... 4. Complicated is better than complex.
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	492 ... 5. Flat is better than nested.
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	493 ... '''.splitlines(1)
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	494 \end{verbatim}
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	495
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	496 Next we instantiate a Differ object:
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	497
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	498 \begin{verbatim}
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	499 >>> d = Differ()
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	500 \end{verbatim}
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	501
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	502 Note that when instantiating a \class{Differ} object we may pass
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	503 functions to filter out line and character ``junk.'' See the
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	504 \method{Differ()} constructor for details.
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	505
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	506 Finally, we compare the two:
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	507
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	508 \begin{verbatim}
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	509 >>> result = d.compare(text1, text2)
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	510 \end{verbatim}
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	511
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	512 \code{result} is a list of strings, so let's pretty-print it:
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	513
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	514 \begin{verbatim}
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	515 >>> from pprint import pprint
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	516 >>> pprint(result)
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	517 [' 1. Beautiful is better than ugly.\n',
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	518 '- 2. Explicit is better than implicit.\n',
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	519 '- 3. Simple is better than complex.\n',
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	520 '+ 3. Simple is better than complex.\n',
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	521 '? ++ \n',
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	522 '- 4. Complex is better than complicated.\n',
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	523 '? ^ ---- ^ \n',
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	524 '+ 4. Complicated is better than complex.\n',
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	525 '? ++++ ^ ^ \n',
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	526 '+ 5. Flat is better than nested.\n']
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	527 \end{verbatim}
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	528
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	529 As a single multi-line string it looks like this:
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	530
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	531 \begin{verbatim}
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	532 >>> import sys
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	533 >>> sys.stdout.writelines(result)
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	534 1. Beautiful is better than ugly.
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	535 - 2. Explicit is better than implicit.
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	536 - 3. Simple is better than complex.
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	537 + 3. Simple is better than complex.
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	538 ? ++
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	539 - 4. Complex is better than complicated.
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	540 ? ^ ---- ^
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	541 + 4. Complicated is better than complex.
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	542 ? ++++ ^ ^
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	543 + 5. Flat is better than nested.
65885ea76c37 David Goodger <dgoodger@atsautomation.com>: Fred Drake <fdrake@acm.org> parents: 17785 diff changeset	544 \end{verbatim}

Mercurial > cpython-lru_cache-weakref

annotate Doc/lib/libdifflib.tex @ 19232:65885ea76c37 legacy-trunk