python-caesar-cipher/main.py at main · Ramtinexe/python-caesar-cipher · GitHub

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art = '''
  CCCCC      AAA     EEEEE    SSSSS     AAA    RRRRR
 C     C    A   A    E       S         A   A   R    R
 C         AAAAAAA   EEE      SSSSS   AAAAAAA  RRRRR
 C         A     A   E             S  A     A  R  R
  CCCCC    A     A   EEEEE    SSSSS   A     A  R   R

  CCCCC    IIIII   PPPP     H   H   EEEEE   RRRR
 C           I     P   P    H   H   E       R   R
 C           I     PPPP     HHHHH   EEE     RRRR
 C           I     P        H   H   E       R  R
  CCCCC    IIIII   P        H   H   EEEEE   R   R

'''

print(art)

# List containing all letters of the alphabet.
alphabet = ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm',
            'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z']


def caesar(original_text, shifter, encode_decode):
    # Reverse the shift when decoding the message.
    if encode_decode == "decode":
        shifter *= -1

    encrypted_text = ""

    # Go through every character in the original message.
    for char in original_text:

        # Only shift characters that exist in the alphabet.
        if char in alphabet:
            index = alphabet.index(char) + shifter

            # Keep the index inside the alphabet using modulo.
            # For example, z shifted by 1 becomes a.
            index %= len(alphabet)

            encrypted_text = encrypted_text + alphabet[index]

        else:
            # Keep spaces and other characters unchanged.
            encrypted_text += char

    print(f"Your {encode_decode} result is :{encrypted_text}")


# Controls whether the program should continue running.
continue_flaged = True

while continue_flaged:

    # Ask the user whether they want to encode or decode a message.
    direction = input(
        "Type 'encode' to encrypt, type 'decode' to decrypt:\n"
    ).lower()

    # Make sure the user entered a valid direction.
    if direction != 'encode' and direction != 'decode':
        print("please enter right input")
        break

    else:
        # Get the message from the user.
        text = input("Type your message:\n").lower()

        # Convert the shift value from a string to an integer.
        # ValueError occurs if the user enters something that isn't a number.
        try:
            shift = int(input("Type the shift number:\n"))
        except ValueError:
            print("Please enter a number")
            break

    # Encrypt or decrypt the message.
    caesar(original_text=text, shifter=shift, encode_decode=direction)

    # Ask the user if they want to use the program again.
    restart_loop = input(
        "Type yes if you want to go again, otherwise type no:\n"
    ).lower()

    # Check if the user entered a valid answer.
    if restart_loop == "yes" or restart_loop == "no":

        if restart_loop == "yes":
            continue_flaged = True

        else:
            continue_flaged = False
            print("Goodbye")

    else:
        print("please enter yes or no")
        continue_flaged = False