Cryptography in Python Caesar Cipher

#Caesar Cipher

MAX_KEY_SIZE = 26

def getMode():
    while True:
        print('Do you wish to encrypt or decrypt a message?')
        mode = input().lower()
        if mode in 'encrypt e decrypt d'.split():
            return mode
        else:
            print("Enter either 'encrypt' or 'e' or 'decrypt' or 'd'")
def getMessage():
    print('Enter your message')
    return input()

def getKey():
    key = 0
    while True:
        print('Enter the key number (1-%s)'%(MAX_KEY_SIZE))
        key=int(input())

        if key>=1 and key<=MAX_KEY_SIZE:
            return key
def getTranslatedMessage(mode,message,key):
    if mode[0] == 'd':
        key=-key
    translated= ''

    for symbol in message:
        if symbol.isalpha():
            num=ord(symbol)
            num+=key

            if symbol.isupper():
                if num>ord('Z'):
                    num-=26
                elif num<ord('A'):
                    num+=26
            elif symbol.islower():
                if num>ord('z'):
                    num-=26
                elif num<ord('a'):
                    num+=26
            translated+=chr(num)
        else:
            translated+=symbol
    return translated


mode = getMode()
message = getMessage()
key = getKey()

print("Your translated text is :")
print(getTranslatedMessage(mode,message,key))