Vigener Cypher

import string

def vigener_cypher(key, message):
    alphabet = string.lowercase
	key *= (len(message) // len(key)) + 1
	translate = lambda x: [alphabet.index(c) for c in x]
	message, key = translate(message), translate(key)
	cypher = [(pair[0] + 1 + pair[1]) % 26 for pair in zip(key, message)]
	cypher = map(lambda c: alphabet[c], cypher)
	return ''.join(cypher)