forairy.py

import string


def encode(phrase):
    final = []

    rot13 = string.maketrans(
            "ABCDEFGHIJKLMabcdefghijklmNOPQRSTUVWXYZnopqrstuwxyz",
            "NOPQRSTUVWXYZnopqrstuwxyzABCDEFGHIJKLMabcdefghijklm"
            )

    for letter in phrase:
        final.append(string.translate(letter, rot13))
    print final


def decode(phrase):
    final = []

    rot13 = string.maketrans(
            "NOPQRSTUVWXYZnopqrstuwxyzABCDEFGHIJKLMabcdefghijklm",
            "ABCDEFGHIJKLMabcdefghijklmNOPQRSTUVWXYZnopqrstuwxyz"
            )

    for letter in phrase:
        final.append(string.translate(letter, rot13))
    print final

def main():
    print "decode or encode?"

    action = raw_input()
    if action == "encode":
        print "enter phrase to encode"
        phrase = raw_input()
        encode(phrase)
    elif action == "decode":
        print "enter phrase to decode"
        phrase = raw_input()
        decode(phrase)
    else:
        "Not an option"

if __name__ == "__main__":
    main()