python-exercises/caesar-cipher.py at main · moorcode/python-exercises · GitHub

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def caesar(text, shift, encrypt=True):

    if not isinstance(shift, int):
        return 'Shift must be an integer value.'

    if shift < 1 or shift > 25:
        return 'Shift must be an integer between 1 and 25.'

    alphabet = 'abcdefghijklmnopqrstuvwxyz'

    if not encrypt:
        shift = - shift

    shifted_alphabet = alphabet[shift:] + alphabet[:shift]
    translation_table = str.maketrans(alphabet + alphabet.upper(), shifted_alphabet + shifted_alphabet.upper())
    encrypted_text = text.translate(translation_table)
    return encrypted_text

def encrypt(text, shift):
    return caesar(text, shift)

def decrypt(text, shift):
    return caesar(text, shift, encrypt=False)
encrypted_text = 'Pbhentr vf sbhaq va hayvxryl cynprf.'
decrypted_text = decrypt(encrypted_text, 13)
print(decrypted_text)