Caesar_Cipher.py

FIRST_CHAR_CODE = ord("A")
LAST_CHAR_CODE = ord("Z")
CHAR_RANGE = LAST_CHAR_CODE - FIRST_CHAR_CODE + 1 #coz index count starts from 0

def caesar_shift(message, shift):
    #result placeholder
    result = ""

    # go through each of the letters in the message.
    for char in message.upper():
        if char.isalpha():
            #convert charc into ASCII code
            char_code = ord(char)
            new_char_code = char_code + shift

            if new_char_code > LAST_CHAR_CODE:
                new_char_code -= CHAR_RANGE

            if new_char_code < FIRST_CHAR_CODE:
                new_char_code += CHAR_RANGE

            new_char = chr(new_char_code)
            result = result + new_char
        else:
            result = result + char

    print(result)

user_message = input("Message to Encrypt: ")
user_shift_key = int(input("Shift Key (int): "))
caesar_shift(user_message, user_shift_key)