| :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 * |
| |
| 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. |
| |
| |
| .. 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. |
| |
| |
| .. 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), end="") |
| - 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)), end="") |
| one |
| two |
| three |
| >>> print(''.join(restore(diff, 2)), end="") |
| 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. |
| |
| |
| .. 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)``. |
| |
| 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! |
| |
| .. 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`. |
| |
| |
| .. 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() |