Caesar

caesar.py

#! /usr/bin/env python3

from string import ascii_uppercase

alphabeth = ascii_uppercase

def caesar(string, key):
    """Given a `string` and a `key`, return-s a string in which every
    character is substituted with the one `key` positions forward in
    the `alphabeth`.

    Function `c` is analogous to chr(), and function `o` to its
    opposite, ord().

    I am thinking of writing this function without relying on the
    "expensive" .find() method, we should use a dictionary where
    cipher-char is the key, and translated is the value, so that we
    can translate with translated = translator[cipher-char].

    """
    import functools

    o = lambda l: alphabeth.find(l)
    c = lambda n: alphabeth[n % len(alphabeth)]
    lettershift = lambda n, l: c(o(l)+n) if l in alphabeth else l
    return ''.join(map(functools.partial(lettershift, key), string))

def caesar2(string, key):
    d = {k: v for k, v in zip(alphabeth, alphabeth[key:] + alphabeth[:key])}
    return ''.join(map(lambda l: d[l] if l in d.keys() else l, string))

def main():
    import sys

    try:
        f = open(sys.argv[1])
    except:
        f = sys.stdin

    text = ''.join(f)
    for i in range(len(alphabeth)):
        for line in text.splitlines():
            print ("{}".format(i).zfill(2), ': ',
                   caesar(line.upper(), i), sep='')

if __name__ == "__main__":
    main()