Example lookup table implementation for regex generator

gistfile1.py

# Create mappings for every character, for instance:
s=['s','5','z','es','2']
alphabet={ 's':s }

def get_permutations(self, letter):
    try:
        permutations = alphabet[letter]
    except KeyError: # The letter is not in alphabet
        permutations = letter
    regex = '['
    for p in permutations[:-1]:
        regex += '{0}|'.format(p)
    regex += '{0}]'.format(permutations[-1])

    return regex