Morse Code Encoder and Decoder

morse_translate.py

""" Morse Code translator """

MORSE = ['..-', '---', '....', '.--', '.---', '-', '--.-', '-..', '...',
         '-..-', '--', '-.', '.-..', '.-', '-.-', '..', '--..', '-.-.', '.--.',
         '--.', '-...', '-..--', '.', '.-.', '..-.', '...-', '/', ' ']
ALPHA = ['u', 'o', 'h', 'w', 'j', 't', 'q', 'd', 's', 'x', 'm', 'n', 'l', 'a',
         'k', 'i', 'z', 'c', 'p', 'g', 'b', 'y', 'e', 'r', 'f', 'v', ' ', '']


def translate(lkp, out, encoded, in_delim, out_delim):
    """
    Translate string from one alphabet to another.

    Returns string with message decoded to the output alphabet

    lkp: List of the lookup alphabet
    out: List of the output alphabet
    encoded: Message encoded in lkp alphabet
    in_delim: Delimiter used in encoded string to separate letters
    out_delim: Delimiter used in decoded string to separate letters
    """
    # format input string
    encoded = encoded.lower()
    if in_delim:
        encoded = encoded.split(in_delim)

    # translate from one alphabet to another
    try:
        encoded = [out[lkp.index(letter)] for letter in encoded]
    except ValueError:
        return None
    else:
        # combine characters with specified output delimiter
        return out_delim.join(encoded)


def main():
    """ Gather and direct input/output """
    print('\nMorse Code Encoder and Decoder')
    print('\t1) Alpha to Morse')
    print('\t2) Morse to Alpha')
    print('\t3) Quit')
    print('')

    while True:
        cmd = input('> ')

        if cmd == "1":
            encoded = input('Alpha String: ')
            decoded = translate(ALPHA, MORSE, encoded, '', ' ')
            if encoded:
                print(decoded)
            else:
                print('Invalid characters.')

        elif cmd == "2":
            encoded = input('Morse String: ')
            decoded = translate(MORSE, ALPHA, encoded, ' ', '')
            if decoded:
                print(decoded)
            else:
                print('Invalid characters.')

        elif cmd == "3":
            print('Goodbye.')
            break

if __name__ == "__main__":
    main()