DoshkoCode

import timeit

def string_match(a, b):
    return sum([max(0, len(m)-1) for m in ''.join(map(lambda x: 'y' if x[0] == x[1] else 'n', zip(a, b))).split('n')])

def test(func):
    assert(func('xxcaazz', 'xxbaaz') == 3)
    assert(func('abc', 'abc') == 2)
    assert(func('abc', 'axc') == 0)
    assert(func('hello', 'he') == 1)
    assert(func('he', 'hello') == 1)
    assert(func('h', 'hello')  == 0)
    assert(func('', 'hello') == 0)
    assert(func('aabbccdd', 'abbbxxd') == 1)
    assert(func('aaxxaaxx', 'iaxxai') == 3)
    assert(func('iaxxai', 'aaxxaaxx') == 3)

def time_test():
    return test(string_match)

print timeit.timeit(time_test, number=10000)