在一个Caeser密码工作，但是文本没有被返回，因为它应该？

Question

每当我输入编码“hello world”的移位量为1时，就会得到“ifmmp xpsme1”，这是正确的。然而，每当我试图解码它，它给我“hello9worldJ”这显然是不正确的。你知道吗

def encryption(string, shift):
    cipher = ''
    for char in string:
        if char == ' ':
            cipher = cipher + char
        elif char.isupper():
            cipher = cipher + chr((ord(char) + shift - 65) % 26 + 65)
        else:
            cipher = cipher + chr((ord(char) + shift - 97) % 26 + 97)
    shift = str(shift)

    return cipher + shift


def cipherDecrypt(word, key):
    decryptString = ""
    for i in word:
        charvalue = ord(i) - key
        if charvalue < 97:
            charvalue = ord("z") - (96-charvalue)
            decryptString += chr(charvalue)
        elif charvalue == 32:
            decryptString += " "
        else:
            decryptString += chr(charvalue)
    return decryptString

def main():
    decision = ""
    while decision != "stop":
        decision = input("Would you like to 'encode' or 'decode' or 'stop': ")
        if decision == "encode":
            text = input("Enter a string to encode: ")
            num = int(input("Enter your number to shift: "))
            print("Original input: ", text)
            print("After encryption: ", encryption(text, num))
        elif decision == "decode":
            text = input("Enter a string to decode: ")
            num = int(input("Enter your number to shift: "))
            print("Original input: ", text)
            print("After encryption: ", cipherDecrypt(text, num))


main()

Answer 1

在你做的时候

        elif charvalue == 32:
            decryptString += " "

您已经将charvalue设置为

        charvalue = ord(i) - key

但是看看你原来的编码字符串：空间在编码时变成了空间，但此时你已经“解码”了一个空间，然后才检查它是什么。你知道吗

你必须这样做：

def cipherDecrypt(word, key):
    decryptString = ""
    for i in word:
        charvalue = ord(i) - key
        if i == 32:  # Check if the character is a space BEFORE decoding it
            decryptString += " "
        elif charvalue < 97:
            charvalue = ord("z") - (96-charvalue)
            decryptString += chr(charvalue)
        else:
            decryptString += chr(charvalue)
    return decryptString

---

但是，仍然存在一些细微的错误；更好的检查是验证每个字符是否可以在继续之前解码：

def cipherEncrypt(word, key):
    cipher = ''
    for char in string:
        if char.isupper():
            cipher += chr((ord(char) + shift - 65) % 26 + 65)
        elif char.islower():
            cipher += chr((ord(char) + shift - 97) % 26 + 97)
        else:
            cipher += char
    return cipher

这样，你就可以对字母进行加密并传递其他信息。你知道吗

另外，考虑到凯撒密码的性质，cipherDecrypt的定义很简单：

def cipherDecrypt(word, key):
    return cipherEncrypt(word, -key)