def decrypt_letter(letter):
"""Decrypts a single letter
letter : character
"""
if not utils.is_letter(letter):
raise CaesarError("`letter` must be a single English \
capital letter.")
A = ord('A')
return chr((factor_inv * (ord(letter) - A - offset)) % 26 + A)
def encrypt_letter(letter):
"""Encypts a sinlge letter
letter : character
"""
if not utils.is_letter(letter):
raise CaesarError("`letter` must be a single English \
capital letter.")
A = ord('A')
return chr((factor * (ord(letter) - A) + offset) % 26 + A)
