generate_permutations.py

#!/usr/bin/python

def generate_permutation(a_count, b_count, c_count, string_length, prefix=""):
    if a_count + b_count + c_count == string_length:
        print prefix
        return

    generate_permutation(a_count + 1, b_count, c_count, string_length, "a" + prefix)
    generate_permutation(a_count, b_count + 1, c_count, string_length, "b" + prefix)
    generate_permutation(a_count, b_count, c_count + 1, string_length, "c" + prefix)

string_length = int(raw_input("Enter the string lenght please >>> "))

generate_permutation(0, 0, 0, string_length)