2.5 Problem 7

import pyperclip

alphabet = 'abcdefghijklmnopqrstuvwxyz'

def main():

    Message = """"though the cold war has passed, decoded soviet cables have intensified the long running debate on
    whether the soviet union employed american citizens as spies"""
    Key = 'venom'
    Mode = 'encrypt'

    if Mode == 'encrypt':
        translated = encryptMessage(Key, Message)
    elif Mode == 'decrypt':
        translated = decryptMessage(Key, Message)

    print('%sed message:' % (Mode.title()))
    print(translated)
    pyperclip.copy(translated)
    print()
    print('The message has been copied.')


def encryptMessage(key, message):
    return translateMessage(key, message, 'encrypt')


def decryptMessage(key, message):
    return translateMessage(key, message, 'decrypt')


def translateMessage(key, message, mode):
    translated = []

    keyIndex = 0
    key = key.upper()

    for symbol in message:
        num = alphabet.find(symbol.upper())
        if num != -1:
            if mode == 'encrypt':
                num += alphabet.find(key[keyIndex])
            elif mode == 'decrypt':
                num -= alphabet.find(key[keyIndex])

            num %= len(alphabet)


            if symbol.isupper():
                translated.append(alphabet[num])
            elif symbol.islower():
                translated.append(alphabet[num].lower())

            keyIndex += 1
            if keyIndex == len(key):
                keyIndex = 0
        else:
            translated.append(symbol)

    return ''.join(translated)

if __name__ == '__main__':
    main()