Function main

src/gamesbyexample/simplesubcipher.py:18–68

()

LETTERS = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ'

def main():
    print('''Simple Substitution Cipher, by Al Sweigart
A simple substitution cipher has a one-to-one translation for each
symbol in the plaintext and each symbol in the ciphertext.''')

    # Let the user specify if they are encrypting or decrypting:
    while True:  # Keep asking until the user enters e or d.
        print('Do you want to (e)ncrypt or (d)ecrypt?')
        response = input('> ').lower()
        if response.startswith('e'):
            myMode = 'encrypt'
            break
        elif response.startswith('d'):
            myMode = 'decrypt'
            break
        print('Please enter the letter e or d.')

    # Let the user specify the key to use:
    while True:  # Keep asking until the user enters a valid key.
        print('Please specify the key to use.')
        if myMode == 'encrypt':
            print('Or enter RANDOM to have one generated for you.')
        response = input('> ').upper()
        if response == 'RANDOM':
            myKey = generateRandomKey()
            print('The key is {}. KEEP THIS SECRET!'.format(myKey))
            break
        else:
            if checkKey(response):
                myKey = response
                break

    # Let the user specify the message to encrypt/decrypt:
    print('Enter the message to {}.'.format(myMode))
    myMessage = input('> ')

    # Perform the encryption/decryption:
    if myMode == 'encrypt':
        translated = encryptMessage(myMessage, myKey)
    elif myMode == 'decrypt':
        translated = decryptMessage(myMessage, myKey)

    # Display the results:
    print('The %sed message is:' % (myMode))
    print(translated)

    try:
        pyperclip.copy(translated)
        print('Full %sed text copied to clipboard.' % (myMode))
    except:
        pass  # Do nothing if pyperclip wasn't installed.


def checkKey(key):