--- rest25/library/difflib.rst	2008-12-19 16:58:07.000000000 +0900
+++ rest262/library/difflib.rst	2009-04-05 05:02:09.000000000 +0900
@@ -1,52 +1,58 @@
-
 :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::
 
-.. % LaTeXification by Fred L. Drake, Jr. <fdrake@acm.org>.
+   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 hashable.  The basic algorithm predates, and is a
+   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.
+   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             |
    +----------+-------------------------------------------+
@@ -113,185 +119,218 @@
 
       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 generator generating
-   the delta lines) in context diff format.
+   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.
 
-   :file:`Tools/scripts/diff.py` is a command-line front-end for this function.
+      >>> 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. ::
+   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 generator generating the delta lines).
+   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. ::
+   :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::
+   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 generator generating
-   the delta lines) in unified diff format.
+   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.
 
-   :file:`Tools/scripts/diff.py` is a command-line front-end for this function.
+      >>> 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/documents/s=1103/ddj8807c/>`_
+   `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:
 
 
@@ -300,246 +339,252 @@
    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 hashable.
+   empty strings.  The elements of both sequences must be :term:`hashable`.
 
-:class:`SequenceMatcher` objects have the following methods:
+   :class:`SequenceMatcher` objects have the following methods:
 
 
-.. method:: SequenceMatcher.set_seqs(a, b)
+   .. method:: set_seqs(a, b)
 
-   Set the two sequences to be compared.
+      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.
+   :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:: SequenceMatcher.set_seq1(a)
+   .. method:: set_seq1(a)
 
-   Set the first sequence to be compared.  The second sequence to be compared is
-   not changed.
+      Set the first sequence to be compared.  The second sequence to be compared
+      is not changed.
 
 
-.. method:: SequenceMatcher.set_seq2(b)
+   .. method:: set_seq2(b)
 
-   Set the second sequence to be compared.  The first sequence to be compared is
-   not changed.
+      Set the second sequence to be compared.  The first sequence to be compared
+      is not changed.
 
 
-.. method:: SequenceMatcher.find_longest_match(alo, ahi, blo, bhi)
+   .. method:: find_longest_match(alo, ahi, blo, bhi)
 
-   Find longest matching block in ``a[alo:ahi]`` and ``b[blo:bhi]``.
+      Find longest matching block in ``a[alo:ahi]`` and ``b[blo:bhi]``.
 
-   If *isjunk* was omitted or ``None``, :meth:`get_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*. ::
+      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)
-      (0, 4, 5)
+         >>> 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.
+      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::
+      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)
-      (1, 0, 4)
+         >>> 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)``.
+      If no blocks match, this returns ``(alo, blo, 0)``.
 
+      .. versionchanged:: 2.6
+         This method returns a :term:`named tuple` ``Match(a, b, size)``.
 
-.. method:: SequenceMatcher.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*.
+   .. method:: get_matching_blocks()
 
-   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.
+      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*.
 
-   .. % Explain why a dummy is used!
+      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.
 
-   .. versionchanged:: 2.5
-      The guarantee that adjacent triples always describe non-adjacent blocks was
-      implemented.
+      .. XXX Explain why a dummy is used!
 
-   ::
+      .. versionchanged:: 2.5
+         The guarantee that adjacent triples always describe non-adjacent blocks
+         was implemented.
 
-      >>> s = SequenceMatcher(None, "abxcd", "abcd")
-      >>> s.get_matching_blocks()
-      [(0, 0, 2), (3, 2, 2), (5, 4, 0)]
+      .. 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:: SequenceMatcher.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*.
+   .. method:: get_opcodes()
 
-   The *tag* values are strings, with these meanings:
+      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*.
 
-   +---------------+---------------------------------------------+
-   | 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).                                 |
-   +---------------+---------------------------------------------+
+      The *tag* values are strings, with these meanings:
 
-   For example::
+      +---------------+---------------------------------------------+
+      | 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).                                 |
+      +---------------+---------------------------------------------+
 
-      >>> 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)
+      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:: SequenceMatcher.get_grouped_opcodes([n])
 
-   Return a generator of groups with up to *n* lines of context.
+   .. method:: get_grouped_opcodes([n])
 
-   Starting with the groups returned by :meth:`get_opcodes`, this method splits out
-   smaller change clusters and eliminates intervening ranges which have no changes.
+      Return a :term:`generator` of groups with up to *n* lines of context.
 
-   The groups are returned in the same format as :meth:`get_opcodes`.
+      Starting with the groups returned by :meth:`get_opcodes`, this method
+      splits out smaller change clusters and eliminates intervening ranges which
+      have no changes.
 
-   .. versionadded:: 2.3
+      The groups are returned in the same format as :meth:`get_opcodes`.
+
+      .. versionadded:: 2.3
 
 
-.. method:: SequenceMatcher.ratio()
+   .. method:: ratio()
 
-   Return a measure of the sequences' similarity as a float in the range [0, 1].
+      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.
+      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.
+      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:: SequenceMatcher.quick_ratio()
+   .. method:: quick_ratio()
 
-   Return an upper bound on :meth:`ratio` relatively quickly.
+      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.
+      This isn't defined beyond that it is an upper bound on :meth:`ratio`, and
+      is faster to compute.
 
 
-.. method:: SequenceMatcher.real_quick_ratio()
+   .. method:: real_quick_ratio()
 
-   Return an upper bound on :meth:`ratio` very quickly.
+      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`.
+      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`::
+: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:" ::
+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::
+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::
+: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 6 elements
-   a[14] and b[23] match for 15 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`::
+: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[8:14] b[17:23]
-    equal a[14:29] b[23:38]
+    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
@@ -554,91 +599,163 @@
 
    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:
+   :class:`Differ` objects are used (deltas generated) via a single method:
 
 
-.. method:: Differ.compare(a, b)
+   .. method:: Differ.compare(a, b)
 
-   Compare two sequences of lines, and generate the delta (a sequence of lines).
+      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.
+      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)::
+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::
+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::
+Finally, we compare the two:
 
    >>> result = list(d.compare(text1, text2))
 
-``result`` is a list of strings, so let's pretty-print it::
+``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',
+    '?     ++\n',
     '-   4. Complex is better than complicated.\n',
-    '?            ^                     ---- ^  \n',
+    '?            ^                     ---- ^\n',
     '+   4. Complicated is better than complex.\n',
-    '?           ++++ ^                      ^  \n',
+    '?           ++++ ^                      ^\n',
     '+   5. Flat is better than nested.\n']
 
-As a single multi-line string it looks like this::
+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()
