Chapter 14 - Caesar Cipher

Chapter Content and Source Code

Download the source for cipher.py.

Or you can copy and paste the code from here:
# Caesar Cipher MAX_KEY_SIZE = 26 def getMode(): while True: print('Do you wish to encrypt or decrypt a message?') mode = input().lower() if mode in 'encrypt e decrypt d'.split(): return mode else: print('Enter either "encrypt" or "e" or "decrypt" or "d".') def getMessage(): print('Enter your message:') return input() def getKey(): key = 0 while True: print('Enter the key number (1-%s)' % (MAX_KEY_SIZE)) key = int(input()) if (key >= 1 and key <= MAX_KEY_SIZE): return key def getTranslatedMessage(mode, message, key): if mode[0] == 'd': key = -key translated = '' for symbol in message: if symbol.isalpha(): num = ord(symbol) num += key if symbol.isupper(): if num > ord('Z'): num -= 26 elif num < ord('A'): num += 26 elif symbol.islower(): if num > ord('z'): num -= 26 elif num < ord('a'): num += 26 translated += chr(num) else: translated += symbol return translated mode = getMode() message = getMessage() key = getKey() print('Your translated text is:') print(getTranslatedMessage(mode, message, key))

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Copyright © 2008, 2009, 2010 by Albert Sweigart
"Invent Your Own Computer Games with Python" 2nd Edition is free to copy and distribute under the Creative Commons Attribution-Noncommercial-Share Alike 3.0 United States License.