Caesar Cipher

caesar.py

from functools import wraps


a_ord = ord('a')


class NonAlphaException(Exception):
    pass

  
def check(func):
    @wraps(func)
    def wrapper(alpha, offset):
        if not alpha.isalpha():
            raise NonAlphaException
        return func(alpha, offset)   
    return wrapper


@check
def encrypt(alpha, offset):
    return chr(a_ord + ((ord(alpha) - a_ord + offset) % 26))

  
@check
def decrypt(alpha, offset):
    return chr(a_ord + ((ord(alpha) - a_ord - offset) % 26))