Caesar Cipher Python

for x in range (2):
# the string to be encrypted/decrypted
    message =input( 'Enter a message')
    translated = ''
    # the encryption/decryption key
    key = int(input("Enter Key"))

    # tells the program to encrypt or decrypt
    mode = input('encrypt or decrypt') .lower()# set to 'encrypt' or 'decrypt'

    # every possible symbol that can be encrypted
    LETTERS = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ'

    # capitalize the string in message
    message = message.upper()

    # run the encryption/decryption code on each symbol in the message string
    for symbol in message:
        if symbol in LETTERS:
            # get the encrypted (or decrypted) number for this symbol
            num = LETTERS.find(symbol) # get the number of the symbol
            if mode == 'encrypt':
                num = num + key
            elif mode == 'decrypt':
                num = num - key

            # add encrypted/decrypted number's symbol at the end of translated
            translated = translated + LETTERS[num]

        else:
            # just add the symbol without encrypting/decrypting
            translated = translated + symbol

    # print the encrypted/decrypted string to the screen
    print(translated)