Caesar Cipher

class caesarCipher:
    def __init__(self, message):
        self._message = message

    def encryptMessage(self, shift):
        encryptedMessage = ""
        for i in self._message.upper():
            if "A" <= i <= "Z":
                encryptedMessage += chr(65 + (ord(i)-65 -shift)%26)
            else:
                encryptedMessage += i
        return encryptedMessage

    def decryptMessage(self, shift):
        decryptedMessage = ""
        for i in self._message.upper():
            if "A" <= i <= "Z":
                decryptedMessage += chr(65 + (ord(i)-65 + shift)%26)
            else:
                decryptedMessage += i
        return decryptedMessage


sifra = caesarCipher("AOXDRQFK JXOGXKLSFZ")
print sifra.decryptMessage(3)

input()