Caesar Cipher - Cryptography in Python

Cryptography - CaesarCipher.py

#Simple Ceasar Cipher - Cryptography

class CaesarCipher:
    #Class for doing ecryption and decryption using Ceasar cipher

    def __init__(self,shifter):
        #Costruct cipher using integer shift of alphabet
        encoderList = [None] * 26
        decoderList = [None] * 26
        for i in range(26):
            encoderList[i] = chr((i + shifter)%26 + ord('A'))
            decoderList[i] = chr((i - shifter)%26 + ord('A'))
        self.forward = ''.join(encoderList)                 #stores as string
        self.backward = ''.join(decoderList)                #since fixed

    def encryptMessage(self, message):
        # Returns string representation of encripted message
        return self.transformMessage(message, self.forward)

    def decryptMessage(self, secret):
        # Return decrypted message given encrypted secret
        return self.transformMessage(secret, self.backward)

    def transformMessage(self, original, code):
        # Utility to perform transformation based on given code string
        msg = list(original)
        for i in range(len(msg)):
            if msg[i].isupper():
                j = ord(msg[i]) - ord('A')  # index from 0 to 25
                msg[i] = code[j]
        return ''.join(msg)

cipher = CaesarCipher(5)
message = "TYPING AN ENCRYPTED MESSAGE"
codedMessage = cipher.encryptMessage(message)
print('Secret: ',codedMessage)
answerKey = cipher.decryptMessage(codedMessage)
print('Message: ',answerKey)