Find all combinations / permutations of a string

combine_permute.py

def combine(s):
    if len(s) <= 1:
        return {'', s}
    last_char = s[-1]
    result = combine(s[:-1])
    intermediate = {i for i in result}
    for item in result:
        intermediate.add(item + last_char)
    return list(intermediate)


def permute(s):
    if len(s) <= 1:
        return {s}
    last_char = s[-1]
    result = set()
    for item in permute(s[:-1]):
        for index in range(len(item) + 1):
            result.add(item[:index] + last_char + item[index:])
    return list(result)