compare lists, see: http://www.python-forum.de/viewtopic.php?f=1&t=29222

compare.py

"""
http://www.python-forum.de/viewtopic.php?f=1&t=29222
"""

import difflib
from itertools import izip_longest, tee


def compare(first, second):
    """
    from Hyperion
    """
    def pairwise(iterable):
        """
        Aus der Doku zu `itertools`
        s -> (s0,s1), (s1,s2), (s2, s3), ...
        """
        a, b = tee(iterable)
        next(b, None)
        return izip_longest(a, b)

    pf, ps = map(pairwise, (first, second))
    f, s = map(next, (pf, ps))
    while True:
        if f[0] != s[0]:
            if f[1] == s[0]:
                yield ("-", f[0])
                f = next(pf)
                continue
            elif f[0] == s[1]:
                yield("+", s[0])
                s = next(ps)
                continue
            yield ("-", f[0])
            yield ("+", s[0])
        else:
            yield (" ", f[0])
        f = next(pf)
        s = next(ps)



def diff(sequence_a, sequence_b):
    """
    BlackJack
    """
    matcher = difflib.SequenceMatcher(a=sequence_a, b=sequence_b)
    for opcode, i, j, m, n in matcher.get_opcodes():
        if opcode == 'equal':
            yield (' ', sequence_a[i:j])
        elif opcode == 'delete':
            yield ('-', sequence_a[i:j])
        elif opcode == 'insert':
            yield ('+', sequence_b[m:n])
        elif opcode == 'replace':
            yield ('-', sequence_a[i:j])
            yield ('+', sequence_b[m:n])
        else:
            assert False, 'unknown opcode %r' % opcode


def set_compare(first, second):
    """
    jens
    """
    result = []
    for item in set(first).union(set(second)):
        tag = None
        if item not in first:
            tag = "+"
        elif item not in second:
            tag = "-"
        else:
            tag = " "
        result.append((tag, item))
    return result


def main():
    old = ['1', '2', '3', 'veer', '7', '8', '9']
    new = ['1', '3', 'vier', '5', '6', '9']

    print "difflib.ndiff():"
    for line in difflib.ndiff(old, new):
        if line and not line.startswith("?"):
            print line

    print "-"*79

    print "difflib.SequenceMatcher():"
    for operation, values in diff(old, new):
        for value in values:
            print operation, value

    print "-"*79

    print "compare used itertools:"
    for operation, value in compare(old, new):
        print operation, value

    print "-"*79

    print "compare used set():"
    for operation, value in set_compare(old, new):
        print operation, value




if __name__ == '__main__':
    main()


#Output:
"""
difflib.ndiff():
  1
- 2
  3
- veer
+ vier
- 7
- 8
+ 5
+ 6
  9
-------------------------------------------------------------------------------
difflib.SequenceMatcher():
  1
- 2
  3
- veer
- 7
- 8
+ vier
+ 5
+ 6
  9
-------------------------------------------------------------------------------
compare used itertools:
  1
- 2
  3
- veer
+ vier
- 7
+ 5
- 8
+ 6
  9
-------------------------------------------------------------------------------
compare used set():
- veer
  1
  3
- 2
+ 5
- 7
+ 6
  9
- 8
+ vier
"""