.py

# Caesar Cipher		
2	# https://inventwithpython.com/hacking (BSD Licensed)		
3		1	
4	import pyperclip		
5			
6	# The string to be encrypted/decrypted:		
7	message = 'This is my secret message.'		
8			
9	# the encryption/decryption key		
10	key = 13		
11			
12	# tells the program to encrypt or decrypt		
13	mode = 'encrypt' # set to 'encrypt' or 'decrypt'		
14			
15	# every possible symbol that can be encrypted		
16	LETTERS = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ'		
17			
18	# stores the encrypted/decrypted form of the message		
19	translated = ''		
20			
21	# capitalize the string in message		
22	message = message.upper()		
23			
24	# run the encryption/decryption code on each symbol in the message string		
25	for symbol in message:		
26	    if symbol in LETTERS:		
27	        # get the encrypted (or decrypted) number for this symbol		
28	        num = LETTERS.find(symbol) # get the number of the symbol		
29	        if mode == 'encrypt':		
30	            num = num + key		
31	        elif mode == 'decrypt':		
32	            num = num - key		
33			
34	        # handle the wrap-around if num is larger than the length of		
35	        # LETTERS or less than 0		
36	        if num >= len(LETTERS):		
37	            num = num - len(LETTERS)		
38	        elif num < 0:		
39	            num = num + len(LETTERS)		
40			
41	        # add encrypted/decrypted number's symbol at the end of translated		
42	        translated = translated + LETTERS[num]		
43			
44	    else:		
45	        # just add the symbol without encrypting/decrypting		
46	        translated = translated + symbol		
47			
48	# print the encrypted/decrypted string to the screen		
49	print(translated)		
50			
51	# copy the encrypted/decrypted string to the clipboard		
52	pyperclip.copy(translated)