Encoding/Decoding Vigenere Cypher

import string
def vigenere(c,k,e=1):
    # e=1 to encrypt, e=-1 to decrypt
    wk=[string.ascii_uppercase.find(ch) for ch in k.upper()]
    wc=[string.ascii_uppercase.find(ch) for ch in c.upper()]
    wc = [ (x[0]+(e*x[1]))%26 for x in zip(wc,wk*(len(wc)/len(wk)+1))]

    return string.join([string.ascii_uppercase[x] for x in wc],"")

vigenere('Encodeme', 'mypassphrase', 1)

'QLROVWBL'

vigenere('QLROVWBL', 'mypassphrase', -1)

'ENCODEME'