itws.py

from functools import reduce, partial
from operator import add

def compose(*fns):
    compose_binary = lambda f, g: lambda x: f(g(x))
    return reduce(compose_binary, fns, lambda x: x)

def edit_distance(s1,s2):
    if len(s1) > len(s2):
        s1,s2 = s2,s1
    distances = range(len(s1) + 1)
    for index2,char2 in enumerate(s2):
        newDistances = [index2+1]
        for index1,char1 in enumerate(s1):
            if char1 == char2:
                newDistances.append(distances[index1])
            else:
                newDistances.append(1 + min((distances[index1],
                                             distances[index1+1],
                                             newDistances[-1])))
        distances = newDistances
    return distances[-1]