def encrypt(message, key1,key2): alph = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ' encrypted = '' for c in message: loc = alph.find(c) encrypted += alph[Mod(key1*loc+key2,26)] print message,'->',encrypted # ENCRYPT MESSAGES encrypt('MYSECRET', 3,0) encrypt('KUCMGZMF', 3.inverse_mod(26),0)