import argparse
from random import choice

letter_string = "abcdefghijklmnopqrstuvwxyz"

parser = argparse.ArgumentParser(description="Alphabet cipher")
parser.add_argument("imp", metavar="filename/text", help="File or text to encode, specify -f if using a file")
parser.add_argument("-k", metavar="key", help="Key, string of 26 letters, each letter must only be used once", default=letter_string)
parser.add_argument("-f", action="store_true", help="Specify if using a file input")
parser.add_argument("-r", action="store_true", help="Use a random key (key will be output)")
parser.add_argument("-s", action="store_true", help="Use a random key, and don't say what the key is.  This will make the output hard to decrypt.")
parser.add_argument("-d", action="store_true", help="Decrypt instead of encrypting")
parser.add_argument("-o", metavar="filename", help="Output to a file", default="")
args = parser.parse_args()


def keygen():
    letters = [l for l in letter_string]
    def nxt():
        n = choice(letters)
        letters.remove(n)
        return n
    key = [nxt() for n in range(len(letters))]
    return key

def strkey(k):
    ks = ""
    for l in k:
        ks += l
    return ks

plaintext = args.imp
if args.f:
    plaintext = open(args.imp).read()
else:
    plaintext = args.imp

if args.r:
    key = keygen()
    if not args.s:
        print "Using Key:  ", strkey(key)
else:
    key = [l for l in args.k]

def encrypt(c):
    return key[ord(c)-ord('a')].upper()

def decrypt(c):
    return letter_string[key.index(c)]

ciphertext = ""

if args.d:
    trans = decrypt
else:
    trans = encrypt

for letter in plaintext.lower():
    try:
        ciphertext += trans(letter)
    except:
        ciphertext += letter

if len(args.o):
    open(args.o, "w+").write(ciphertext)
else:
    print ciphertext


Final password:  16f13b876