More difflib examples. Written for GHOP by Josip Dzolonga.

Doc/library/difflib.rst

@@ -148,7 +148,27 @@ diffs. For comparing directories and files, see also, the :mod:`filecmp` module.
    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)
+      *** 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
 
@@ -265,7 +285,25 @@ diffs. For comparing directories and files, see also, the :mod:`filecmp` module.
    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)
+      --- 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
 
@@ -649,3 +687,75 @@ As a single multi-line string it looks like this::
    ?           ++++ ^                      ^
    +   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`.
+
+::
+
+   """ 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()