def swap(string, first, second, begin, end):
    string[begin] = second
    string[end] = first


def permutate(string, begin = 0):
    end = len(string) -1
    srange = end - begin
    if srange == 1:
        print string
    else:
        for i in range(0, srange):
            swap(string, string[begin], string[begin+i], begin, begin+i)
            permutate(string, begin+1)
            swap(string, string[begin], string[begin+i], begin, begin+i)

Python Pre 2.6 Permutation

Python