a (functional) python 3.x vigenere encoder / decoder.

vigenere.py

# ben oliver 11.01.2013
# a (functional) python 3.x vigenere encoder / decoder.
# encode and decode functions are mathematical, no dictionary lookups.

from itertools import cycle
from functools import partial
from string import ascii_uppercase

def transform(crypt_function,k,s):
    """ (Int -> Int -> Int) -> Char -> Char -> Char """
    return chr(crypt_function(ord(k), ord(s)))

def encode26(a,b):
    """ Int -> Int -> Int """
    return (((a + b) - 130) % 26) + 65
 
def decode26(a,b):
    """ Int -> Int -> Int """
    return (((b - a) - 130) % 26) + 65

def cipher(crypt_function,key,string):
    """ (Int -> Int -> Int) -> String -> String -> String """
    transform_function = partial(transform, crypt_function)
    mapped_transform = map(transform_function, cycle(key), string)
    return ''.join(mapped_transform)

def safe_cipher(crypt_function,key,string):
    """ (Int -> Int -> Int) -> String -> String -> (String,String) 
    converts lowercase to uppercase , removing digits, whitespace & punctuation"""
    k = ''.join(filter(lambda k: k in ascii_uppercase, key.upper()))
    s = ''.join(filter(lambda s: s in ascii_uppercase, string.upper()))
    return (k, cipher(crypt_function,k,s))


### example ##################################################################################
# >>> (password,encoded) = safe_cipher( encode26, "password", "This... is the string to encode!!!" )
# >>> cipher(decode26,password,encoded)
# 'THISISTHESTRINGTOENCODE'