caesar_cipher.py

#This program takes in input from user and encodes the message using a Caesar Cipher.

from enum import IntEnum

class Action(IntEnum):
    Encrypt = 0
    Decrypt = 1

def get_user_choice():
    choices = [f"{action.name}[{action.value}]" for action in Action]
    choices_str=",".join(choices)
    selection=int(input(f"Enter a choice to either encrypt or decrypt a caeser cipher message ({choices_str}): "))
    action=Action(selection)
    return action
    

def caesar_cipher(message,encryption_key):
    result = ""
    for i, letter in enumerate(message):
       if (letter.isupper()):
           result += chr((ord(letter) + int(encryption_key)-65) % 26 + 65)
       else:
           result += chr((ord(letter) + int(encryption_key) - 97) % 26 + 97)
    return result

def main():
    while True:
        try:
            user_choice = get_user_choice()
        except ValueError as e:
            range_str = f"[0, {len(Action) - 1}]"
            print(f"Invalid selection. Enter a value in range {range_str}")
            continue
    
        if user_choice==Action.Encrypt:
            print("Enter a message to encrypt.")
            message= input()
            print("Enter a shift key.")
            encryption_key=input()
            print ("Plain message : " + message)
            print ("Shift pattern : " + encryption_key)
            encrypted_message=caesar_cipher(message,encryption_key)
            print( "Cipher: " + encrypted_message)

        else:
            print("Decrypt a caesar cipher message by entering the encrypted message and the shift key")
            print("Enter a encrypted message: ")
            inputed_encrypted_message=input()
            print("Enter the Caesar Cipher shift key: ")
            inputed_encryption_key=input()
            decrypted_message=caesar_cipher(inputed_encrypted_message, (26-(int(inputed_encryption_key))))
            print(decrypted_message)

        keep_going=input("Do yo want to encrypt or decrpty another message? (y/n): ")
        if keep_going.lower() !="y":
            break

# __name__
if __name__=="__main__":
    main()