/Doc/library/difflib.rst
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- :mod:`difflib` --- Helpers for computing deltas
- ===============================================
- .. module:: difflib
- :synopsis: Helpers for computing differences between objects.
- .. moduleauthor:: Tim Peters <tim_one@users.sourceforge.net>
- .. sectionauthor:: Tim Peters <tim_one@users.sourceforge.net>
- .. Markup by Fred L. Drake, Jr. <fdrake@acm.org>
- .. testsetup::
- import sys
- from difflib import *
- .. versionadded:: 2.1
- This module provides classes and functions for comparing sequences. It
- can be used for example, for comparing files, and can produce difference
- information in various formats, including HTML and context and unified
- diffs. For comparing directories and files, see also, the :mod:`filecmp` module.
- .. class:: SequenceMatcher
- This is a flexible class for comparing pairs of sequences of any type, so long
- as the sequence elements are :term:`hashable`. The basic algorithm predates, and is a
- little fancier than, an algorithm published in the late 1980's by Ratcliff and
- Obershelp under the hyperbolic name "gestalt pattern matching." The idea is to
- find the longest contiguous matching subsequence that contains no "junk"
- elements (the Ratcliff and Obershelp algorithm doesn't address junk). The same
- idea is then applied recursively to the pieces of the sequences to the left and
- to the right of the matching subsequence. This does not yield minimal edit
- sequences, but does tend to yield matches that "look right" to people.
- **Timing:** The basic Ratcliff-Obershelp algorithm is cubic time in the worst
- case and quadratic time in the expected case. :class:`SequenceMatcher` is
- quadratic time for the worst case and has expected-case behavior dependent in a
- complicated way on how many elements the sequences have in common; best case
- time is linear.
- .. class:: Differ
- This is a class for comparing sequences of lines of text, and producing
- human-readable differences or deltas. Differ uses :class:`SequenceMatcher`
- both to compare sequences of lines, and to compare sequences of characters
- within similar (near-matching) lines.
- Each line of a :class:`Differ` delta begins with a two-letter code:
- +----------+-------------------------------------------+
- | Code | Meaning |
- +==========+===========================================+
- | ``'- '`` | line unique to sequence 1 |
- +----------+-------------------------------------------+
- | ``'+ '`` | line unique to sequence 2 |
- +----------+-------------------------------------------+
- | ``' '`` | line common to both sequences |
- +----------+-------------------------------------------+
- | ``'? '`` | line not present in either input sequence |
- +----------+-------------------------------------------+
- Lines beginning with '``?``' attempt to guide the eye to intraline differences,
- and were not present in either input sequence. These lines can be confusing if
- the sequences contain tab characters.
- .. class:: HtmlDiff
- This class can be used to create an HTML table (or a complete HTML file
- containing the table) showing a side by side, line by line comparison of text
- with inter-line and intra-line change highlights. The table can be generated in
- either full or contextual difference mode.
- The constructor for this class is:
- .. function:: __init__([tabsize][, wrapcolumn][, linejunk][, charjunk])
- Initializes instance of :class:`HtmlDiff`.
- *tabsize* is an optional keyword argument to specify tab stop spacing and
- defaults to ``8``.
- *wrapcolumn* is an optional keyword to specify column number where lines are
- broken and wrapped, defaults to ``None`` where lines are not wrapped.
- *linejunk* and *charjunk* are optional keyword arguments passed into ``ndiff()``
- (used by :class:`HtmlDiff` to generate the side by side HTML differences). See
- ``ndiff()`` documentation for argument default values and descriptions.
- The following methods are public:
- .. function:: make_file(fromlines, tolines [, fromdesc][, todesc][, context][, numlines])
- Compares *fromlines* and *tolines* (lists of strings) and returns a string which
- is a complete HTML file containing a table showing line by line differences with
- inter-line and intra-line changes highlighted.
- *fromdesc* and *todesc* are optional keyword arguments to specify from/to file
- column header strings (both default to an empty string).
- *context* and *numlines* are both optional keyword arguments. Set *context* to
- ``True`` when contextual differences are to be shown, else the default is
- ``False`` to show the full files. *numlines* defaults to ``5``. When *context*
- is ``True`` *numlines* controls the number of context lines which surround the
- difference highlights. When *context* is ``False`` *numlines* controls the
- number of lines which are shown before a difference highlight when using the
- "next" hyperlinks (setting to zero would cause the "next" hyperlinks to place
- the next difference highlight at the top of the browser without any leading
- context).
- .. function:: make_table(fromlines, tolines [, fromdesc][, todesc][, context][, numlines])
- Compares *fromlines* and *tolines* (lists of strings) and returns a string which
- is a complete HTML table showing line by line differences with inter-line and
- intra-line changes highlighted.
- The arguments for this method are the same as those for the :meth:`make_file`
- method.
- :file:`Tools/scripts/diff.py` is a command-line front-end to this class and
- contains a good example of its use.
- .. versionadded:: 2.4
- .. function:: context_diff(a, b[, fromfile][, tofile][, fromfiledate][, tofiledate][, n][, lineterm])
- Compare *a* and *b* (lists of strings); return a delta (a :term:`generator`
- generating the delta lines) in context diff format.
- Context diffs are a compact way of showing just the lines that have changed plus
- a few lines of context. The changes are shown in a before/after style. The
- number of context lines is set by *n* which defaults to three.
- By default, the diff control lines (those with ``***`` or ``---``) are created
- with a trailing newline. This is helpful so that inputs created from
- :func:`file.readlines` result in diffs that are suitable for use with
- :func:`file.writelines` since both the inputs and outputs have trailing
- newlines.
- For inputs that do not have trailing newlines, set the *lineterm* argument to
- ``""`` so that the output will be uniformly newline free.
- The context diff format normally has a header for filenames and modification
- times. Any or all of these may be specified using strings for *fromfile*,
- *tofile*, *fromfiledate*, and *tofiledate*. The modification times are normally
- expressed in the format returned by :func:`time.ctime`. If not specified, the
- strings default to blanks.
- >>> s1 = ['bacon\n', 'eggs\n', 'ham\n', 'guido\n']
- >>> s2 = ['python\n', 'eggy\n', 'hamster\n', 'guido\n']
- >>> for line in context_diff(s1, s2, fromfile='before.py', tofile='after.py'):
- ... sys.stdout.write(line) # doctest: +NORMALIZE_WHITESPACE
- *** before.py
- --- after.py
- ***************
- *** 1,4 ****
- ! bacon
- ! eggs
- ! ham
- guido
- --- 1,4 ----
- ! python
- ! eggy
- ! hamster
- guido
- See :ref:`difflib-interface` for a more detailed example.
- .. versionadded:: 2.3
- .. function:: get_close_matches(word, possibilities[, n][, cutoff])
- Return a list of the best "good enough" matches. *word* is a sequence for which
- close matches are desired (typically a string), and *possibilities* is a list of
- sequences against which to match *word* (typically a list of strings).
- Optional argument *n* (default ``3``) is the maximum number of close matches to
- return; *n* must be greater than ``0``.
- Optional argument *cutoff* (default ``0.6``) is a float in the range [0, 1].
- Possibilities that don't score at least that similar to *word* are ignored.
- The best (no more than *n*) matches among the possibilities are returned in a
- list, sorted by similarity score, most similar first.
- >>> get_close_matches('appel', ['ape', 'apple', 'peach', 'puppy'])
- ['apple', 'ape']
- >>> import keyword
- >>> get_close_matches('wheel', keyword.kwlist)
- ['while']
- >>> get_close_matches('apple', keyword.kwlist)
- []
- >>> get_close_matches('accept', keyword.kwlist)
- ['except']
- .. function:: ndiff(a, b[, linejunk][, charjunk])
- Compare *a* and *b* (lists of strings); return a :class:`Differ`\ -style
- delta (a :term:`generator` generating the delta lines).
- Optional keyword parameters *linejunk* and *charjunk* are for filter functions
- (or ``None``):
- *linejunk*: A function that accepts a single string argument, and returns true
- if the string is junk, or false if not. The default is (``None``), starting with
- Python 2.3. Before then, the default was the module-level function
- :func:`IS_LINE_JUNK`, which filters out lines without visible characters, except
- for at most one pound character (``'#'``). As of Python 2.3, the underlying
- :class:`SequenceMatcher` class does a dynamic analysis of which lines are so
- frequent as to constitute noise, and this usually works better than the pre-2.3
- default.
- *charjunk*: A function that accepts a character (a string of length 1), and
- returns if the character is junk, or false if not. The default is module-level
- function :func:`IS_CHARACTER_JUNK`, which filters out whitespace characters (a
- blank or tab; note: bad idea to include newline in this!).
- :file:`Tools/scripts/ndiff.py` is a command-line front-end to this function.
- >>> diff = ndiff('one\ntwo\nthree\n'.splitlines(1),
- ... 'ore\ntree\nemu\n'.splitlines(1))
- >>> print ''.join(diff),
- - one
- ? ^
- + ore
- ? ^
- - two
- - three
- ? -
- + tree
- + emu
- .. function:: restore(sequence, which)
- Return one of the two sequences that generated a delta.
- Given a *sequence* produced by :meth:`Differ.compare` or :func:`ndiff`, extract
- lines originating from file 1 or 2 (parameter *which*), stripping off line
- prefixes.
- Example:
- >>> diff = ndiff('one\ntwo\nthree\n'.splitlines(1),
- ... 'ore\ntree\nemu\n'.splitlines(1))
- >>> diff = list(diff) # materialize the generated delta into a list
- >>> print ''.join(restore(diff, 1)),
- one
- two
- three
- >>> print ''.join(restore(diff, 2)),
- ore
- tree
- emu
- .. function:: unified_diff(a, b[, fromfile][, tofile][, fromfiledate][, tofiledate][, n][, lineterm])
- Compare *a* and *b* (lists of strings); return a delta (a :term:`generator`
- generating the delta lines) in unified diff format.
- Unified diffs are a compact way of showing just the lines that have changed plus
- a few lines of context. The changes are shown in a inline style (instead of
- separate before/after blocks). The number of context lines is set by *n* which
- defaults to three.
- By default, the diff control lines (those with ``---``, ``+++``, or ``@@``) are
- created with a trailing newline. This is helpful so that inputs created from
- :func:`file.readlines` result in diffs that are suitable for use with
- :func:`file.writelines` since both the inputs and outputs have trailing
- newlines.
- For inputs that do not have trailing newlines, set the *lineterm* argument to
- ``""`` so that the output will be uniformly newline free.
- The context diff format normally has a header for filenames and modification
- times. Any or all of these may be specified using strings for *fromfile*,
- *tofile*, *fromfiledate*, and *tofiledate*. The modification times are normally
- expressed in the format returned by :func:`time.ctime`. If not specified, the
- strings default to blanks.
- >>> s1 = ['bacon\n', 'eggs\n', 'ham\n', 'guido\n']
- >>> s2 = ['python\n', 'eggy\n', 'hamster\n', 'guido\n']
- >>> for line in unified_diff(s1, s2, fromfile='before.py', tofile='after.py'):
- ... sys.stdout.write(line) # doctest: +NORMALIZE_WHITESPACE
- --- before.py
- +++ after.py
- @@ -1,4 +1,4 @@
- -bacon
- -eggs
- -ham
- +python
- +eggy
- +hamster
- guido
- See :ref:`difflib-interface` for a more detailed example.
- .. versionadded:: 2.3
- .. function:: IS_LINE_JUNK(line)
- Return true for ignorable lines. The line *line* is ignorable if *line* is
- blank or contains a single ``'#'``, otherwise it is not ignorable. Used as a
- default for parameter *linejunk* in :func:`ndiff` before Python 2.3.
- .. function:: IS_CHARACTER_JUNK(ch)
- Return true for ignorable characters. The character *ch* is ignorable if *ch*
- is a space or tab, otherwise it is not ignorable. Used as a default for
- parameter *charjunk* in :func:`ndiff`.
- .. seealso::
- `Pattern Matching: The Gestalt Approach <http://www.ddj.com/184407970?pgno=5>`_
- Discussion of a similar algorithm by John W. Ratcliff and D. E. Metzener. This
- was published in `Dr. Dobb's Journal <http://www.ddj.com/>`_ in July, 1988.
- .. _sequence-matcher:
- SequenceMatcher Objects
- -----------------------
- The :class:`SequenceMatcher` class has this constructor:
- .. class:: SequenceMatcher([isjunk[, a[, b]]])
- Optional argument *isjunk* must be ``None`` (the default) or a one-argument
- function that takes a sequence element and returns true if and only if the
- element is "junk" and should be ignored. Passing ``None`` for *isjunk* is
- equivalent to passing ``lambda x: 0``; in other words, no elements are ignored.
- For example, pass::
- lambda x: x in " \t"
- if you're comparing lines as sequences of characters, and don't want to synch up
- on blanks or hard tabs.
- The optional arguments *a* and *b* are sequences to be compared; both default to
- empty strings. The elements of both sequences must be :term:`hashable`.
- :class:`SequenceMatcher` objects have the following methods:
- .. method:: set_seqs(a, b)
- Set the two sequences to be compared.
- :class:`SequenceMatcher` computes and caches detailed information about the
- second sequence, so if you want to compare one sequence against many
- sequences, use :meth:`set_seq2` to set the commonly used sequence once and
- call :meth:`set_seq1` repeatedly, once for each of the other sequences.
- .. method:: set_seq1(a)
- Set the first sequence to be compared. The second sequence to be compared
- is not changed.
- .. method:: set_seq2(b)
- Set the second sequence to be compared. The first sequence to be compared
- is not changed.
- .. method:: find_longest_match(alo, ahi, blo, bhi)
- Find longest matching block in ``a[alo:ahi]`` and ``b[blo:bhi]``.
- If *isjunk* was omitted or ``None``, :meth:`find_longest_match` returns
- ``(i, j, k)`` such that ``a[i:i+k]`` is equal to ``b[j:j+k]``, where ``alo
- <= i <= i+k <= ahi`` and ``blo <= j <= j+k <= bhi``. For all ``(i', j',
- k')`` meeting those conditions, the additional conditions ``k >= k'``, ``i
- <= i'``, and if ``i == i'``, ``j <= j'`` are also met. In other words, of
- all maximal matching blocks, return one that starts earliest in *a*, and
- of all those maximal matching blocks that start earliest in *a*, return
- the one that starts earliest in *b*.
- >>> s = SequenceMatcher(None, " abcd", "abcd abcd")
- >>> s.find_longest_match(0, 5, 0, 9)
- Match(a=0, b=4, size=5)
- If *isjunk* was provided, first the longest matching block is determined
- as above, but with the additional restriction that no junk element appears
- in the block. Then that block is extended as far as possible by matching
- (only) junk elements on both sides. So the resulting block never matches
- on junk except as identical junk happens to be adjacent to an interesting
- match.
- Here's the same example as before, but considering blanks to be junk. That
- prevents ``' abcd'`` from matching the ``' abcd'`` at the tail end of the
- second sequence directly. Instead only the ``'abcd'`` can match, and
- matches the leftmost ``'abcd'`` in the second sequence:
- >>> s = SequenceMatcher(lambda x: x==" ", " abcd", "abcd abcd")
- >>> s.find_longest_match(0, 5, 0, 9)
- Match(a=1, b=0, size=4)
- If no blocks match, this returns ``(alo, blo, 0)``.
- .. versionchanged:: 2.6
- This method returns a :term:`named tuple` ``Match(a, b, size)``.
- .. method:: get_matching_blocks()
- Return list of triples describing matching subsequences. Each triple is of
- the form ``(i, j, n)``, and means that ``a[i:i+n] == b[j:j+n]``. The
- triples are monotonically increasing in *i* and *j*.
- The last triple is a dummy, and has the value ``(len(a), len(b), 0)``. It
- is the only triple with ``n == 0``. If ``(i, j, n)`` and ``(i', j', n')``
- are adjacent triples in the list, and the second is not the last triple in
- the list, then ``i+n != i'`` or ``j+n != j'``; in other words, adjacent
- triples always describe non-adjacent equal blocks.
- .. XXX Explain why a dummy is used!
- .. versionchanged:: 2.5
- The guarantee that adjacent triples always describe non-adjacent blocks
- was implemented.
- .. doctest::
- >>> s = SequenceMatcher(None, "abxcd", "abcd")
- >>> s.get_matching_blocks()
- [Match(a=0, b=0, size=2), Match(a=3, b=2, size=2), Match(a=5, b=4, size=0)]
- .. method:: get_opcodes()
- Return list of 5-tuples describing how to turn *a* into *b*. Each tuple is
- of the form ``(tag, i1, i2, j1, j2)``. The first tuple has ``i1 == j1 ==
- 0``, and remaining tuples have *i1* equal to the *i2* from the preceding
- tuple, and, likewise, *j1* equal to the previous *j2*.
- The *tag* values are strings, with these meanings:
- +---------------+---------------------------------------------+
- | Value | Meaning |
- +===============+=============================================+
- | ``'replace'`` | ``a[i1:i2]`` should be replaced by |
- | | ``b[j1:j2]``. |
- +---------------+---------------------------------------------+
- | ``'delete'`` | ``a[i1:i2]`` should be deleted. Note that |
- | | ``j1 == j2`` in this case. |
- +---------------+---------------------------------------------+
- | ``'insert'`` | ``b[j1:j2]`` should be inserted at |
- | | ``a[i1:i1]``. Note that ``i1 == i2`` in |
- | | this case. |
- +---------------+---------------------------------------------+
- | ``'equal'`` | ``a[i1:i2] == b[j1:j2]`` (the sub-sequences |
- | | are equal). |
- +---------------+---------------------------------------------+
- For example:
- >>> a = "qabxcd"
- >>> b = "abycdf"
- >>> s = SequenceMatcher(None, a, b)
- >>> for tag, i1, i2, j1, j2 in s.get_opcodes():
- ... print ("%7s a[%d:%d] (%s) b[%d:%d] (%s)" %
- ... (tag, i1, i2, a[i1:i2], j1, j2, b[j1:j2]))
- delete a[0:1] (q) b[0:0] ()
- equal a[1:3] (ab) b[0:2] (ab)
- replace a[3:4] (x) b[2:3] (y)
- equal a[4:6] (cd) b[3:5] (cd)
- insert a[6:6] () b[5:6] (f)
- .. method:: get_grouped_opcodes([n])
- Return a :term:`generator` of groups with up to *n* lines of context.
- Starting with the groups returned by :meth:`get_opcodes`, this method
- splits out smaller change clusters and eliminates intervening ranges which
- have no changes.
- The groups are returned in the same format as :meth:`get_opcodes`.
- .. versionadded:: 2.3
- .. method:: ratio()
- Return a measure of the sequences' similarity as a float in the range [0,
- 1].
- Where T is the total number of elements in both sequences, and M is the
- number of matches, this is 2.0\*M / T. Note that this is ``1.0`` if the
- sequences are identical, and ``0.0`` if they have nothing in common.
- This is expensive to compute if :meth:`get_matching_blocks` or
- :meth:`get_opcodes` hasn't already been called, in which case you may want
- to try :meth:`quick_ratio` or :meth:`real_quick_ratio` first to get an
- upper bound.
- .. method:: quick_ratio()
- Return an upper bound on :meth:`ratio` relatively quickly.
- This isn't defined beyond that it is an upper bound on :meth:`ratio`, and
- is faster to compute.
- .. method:: real_quick_ratio()
- Return an upper bound on :meth:`ratio` very quickly.
- This isn't defined beyond that it is an upper bound on :meth:`ratio`, and
- is faster to compute than either :meth:`ratio` or :meth:`quick_ratio`.
- The three methods that return the ratio of matching to total characters can give
- different results due to differing levels of approximation, although
- :meth:`quick_ratio` and :meth:`real_quick_ratio` are always at least as large as
- :meth:`ratio`:
- >>> s = SequenceMatcher(None, "abcd", "bcde")
- >>> s.ratio()
- 0.75
- >>> s.quick_ratio()
- 0.75
- >>> s.real_quick_ratio()
- 1.0
- .. _sequencematcher-examples:
- SequenceMatcher Examples
- ------------------------
- This example compares two strings, considering blanks to be "junk:"
- >>> s = SequenceMatcher(lambda x: x == " ",
- ... "private Thread currentThread;",
- ... "private volatile Thread currentThread;")
- :meth:`ratio` returns a float in [0, 1], measuring the similarity of the
- sequences. As a rule of thumb, a :meth:`ratio` value over 0.6 means the
- sequences are close matches:
- >>> print round(s.ratio(), 3)
- 0.866
- If you're only interested in where the sequences match,
- :meth:`get_matching_blocks` is handy:
- >>> for block in s.get_matching_blocks():
- ... print "a[%d] and b[%d] match for %d elements" % block
- a[0] and b[0] match for 8 elements
- a[8] and b[17] match for 21 elements
- a[29] and b[38] match for 0 elements
- Note that the last tuple returned by :meth:`get_matching_blocks` is always a
- dummy, ``(len(a), len(b), 0)``, and this is the only case in which the last
- tuple element (number of elements matched) is ``0``.
- If you want to know how to change the first sequence into the second, use
- :meth:`get_opcodes`:
- >>> for opcode in s.get_opcodes():
- ... print "%6s a[%d:%d] b[%d:%d]" % opcode
- equal a[0:8] b[0:8]
- insert a[8:8] b[8:17]
- equal a[8:29] b[17:38]
- See also the function :func:`get_close_matches` in this module, which shows how
- simple code building on :class:`SequenceMatcher` can be used to do useful work.
- .. _differ-objects:
- Differ Objects
- --------------
- Note that :class:`Differ`\ -generated deltas make no claim to be **minimal**
- diffs. To the contrary, minimal diffs are often counter-intuitive, because they
- synch up anywhere possible, sometimes accidental matches 100 pages apart.
- Restricting synch points to contiguous matches preserves some notion of
- locality, at the occasional cost of producing a longer diff.
- The :class:`Differ` class has this constructor:
- .. class:: Differ([linejunk[, charjunk]])
- Optional keyword parameters *linejunk* and *charjunk* are for filter functions
- (or ``None``):
- *linejunk*: A function that accepts a single string argument, and returns true
- if the string is junk. The default is ``None``, meaning that no line is
- considered junk.
- *charjunk*: A function that accepts a single character argument (a string of
- length 1), and returns true if the character is junk. The default is ``None``,
- meaning that no character is considered junk.
- :class:`Differ` objects are used (deltas generated) via a single method:
- .. method:: Differ.compare(a, b)
- Compare two sequences of lines, and generate the delta (a sequence of lines).
- Each sequence must contain individual single-line strings ending with newlines.
- Such sequences can be obtained from the :meth:`readlines` method of file-like
- objects. The delta generated also consists of newline-terminated strings, ready
- to be printed as-is via the :meth:`writelines` method of a file-like object.
- .. _differ-examples:
- Differ Example
- --------------
- This example compares two texts. First we set up the texts, sequences of
- individual single-line strings ending with newlines (such sequences can also be
- obtained from the :meth:`readlines` method of file-like objects):
- >>> text1 = ''' 1. Beautiful is better than ugly.
- ... 2. Explicit is better than implicit.
- ... 3. Simple is better than complex.
- ... 4. Complex is better than complicated.
- ... '''.splitlines(1)
- >>> len(text1)
- 4
- >>> text1[0][-1]
- '\n'
- >>> text2 = ''' 1. Beautiful is better than ugly.
- ... 3. Simple is better than complex.
- ... 4. Complicated is better than complex.
- ... 5. Flat is better than nested.
- ... '''.splitlines(1)
- Next we instantiate a Differ object:
- >>> d = Differ()
- Note that when instantiating a :class:`Differ` object we may pass functions to
- filter out line and character "junk." See the :meth:`Differ` constructor for
- details.
- Finally, we compare the two:
- >>> result = list(d.compare(text1, text2))
- ``result`` is a list of strings, so let's pretty-print it:
- >>> from pprint import pprint
- >>> pprint(result)
- [' 1. Beautiful is better than ugly.\n',
- '- 2. Explicit is better than implicit.\n',
- '- 3. Simple is better than complex.\n',
- '+ 3. Simple is better than complex.\n',
- '? ++\n',
- '- 4. Complex is better than complicated.\n',
- '? ^ ---- ^\n',
- '+ 4. Complicated is better than complex.\n',
- '? ++++ ^ ^\n',
- '+ 5. Flat is better than nested.\n']
- As a single multi-line string it looks like this:
- >>> import sys
- >>> sys.stdout.writelines(result)
- 1. Beautiful is better than ugly.
- - 2. Explicit is better than implicit.
- - 3. Simple is better than complex.
- + 3. Simple is better than complex.
- ? ++
- - 4. Complex is better than complicated.
- ? ^ ---- ^
- + 4. Complicated is better than complex.
- ? ++++ ^ ^
- + 5. Flat is better than nested.
- .. _difflib-interface:
- A command-line interface to difflib
- -----------------------------------
- This example shows how to use difflib to create a ``diff``-like utility.
- It is also contained in the Python source distribution, as
- :file:`Tools/scripts/diff.py`.
- .. testcode::
- """ Command line interface to difflib.py providing diffs in four formats:
- * ndiff: lists every line and highlights interline changes.
- * context: highlights clusters of changes in a before/after format.
- * unified: highlights clusters of changes in an inline format.
- * html: generates side by side comparison with change highlights.
- """
- import sys, os, time, difflib, optparse
- def main():
- # Configure the option parser
- usage = "usage: %prog [options] fromfile tofile"
- parser = optparse.OptionParser(usage)
- parser.add_option("-c", action="store_true", default=False,
- help='Produce a context format diff (default)')
- parser.add_option("-u", action="store_true", default=False,
- help='Produce a unified format diff')
- hlp = 'Produce HTML side by side diff (can use -c and -l in conjunction)'
- parser.add_option("-m", action="store_true", default=False, help=hlp)
- parser.add_option("-n", action="store_true", default=False,
- help='Produce a ndiff format diff')
- parser.add_option("-l", "--lines", type="int", default=3,
- help='Set number of context lines (default 3)')
- (options, args) = parser.parse_args()
- if len(args) == 0:
- parser.print_help()
- sys.exit(1)
- if len(args) != 2:
- parser.error("need to specify both a fromfile and tofile")
- n = options.lines
- fromfile, tofile = args # as specified in the usage string
- # we're passing these as arguments to the diff function
- fromdate = time.ctime(os.stat(fromfile).st_mtime)
- todate = time.ctime(os.stat(tofile).st_mtime)
- fromlines = open(fromfile, 'U').readlines()
- tolines = open(tofile, 'U').readlines()
- if options.u:
- diff = difflib.unified_diff(fromlines, tolines, fromfile, tofile,
- fromdate, todate, n=n)
- elif options.n:
- diff = difflib.ndiff(fromlines, tolines)
- elif options.m:
- diff = difflib.HtmlDiff().make_file(fromlines, tolines, fromfile,
- tofile, context=options.c,
- numlines=n)
- else:
- diff = difflib.context_diff(fromlines, tolines, fromfile, tofile,
- fromdate, todate, n=n)
- # we're using writelines because diff is a generator
- sys.stdout.writelines(diff)
- if __name__ == '__main__':
- main()