带有随机键和空格的凯撒密码代码问题

Question

def message():
    answer = input('Welcome to the Caesar Cipher! What do you want to encrypt?')
    key = input('Enter the key number that you want to encrypt with. (1 - 25)')
    return answer, int(key)


def getMessage(answer, key):
    lengthList = []
    leng = 0
    while leng < len(answer):
        lengthList.append(chr(ord(answer[leng]) + key))
        leng += 1
    print("By the way, random keys are spaces.")
    print("".join(lengthList))


answer, key = message()
getMessage(answer, key)

这是我的Caesar Cipher Encryption Only代码，而我的问题是，有时当我输入消息时，某些字母会变成不同的符号，而不是字母。如何使打印的消息仅包含密钥？我还需要帮助，如果有空格，它也会变成另一个符号。您还如何使这些空间成为空间？