Caesar Cipher in python

问题:

The error which i am getting is

Traceback (most recent call last):
  File "imp.py", line 52, in <module>
    mode = getMode()
  File "imp.py", line 8, in getMode
    mode = input().lower()
  File "<string>", line 1, in <module>
NameError: name 'encrypt' is not defined

Below is the code.

# 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))

回答1:

The problem is here:

print('Do you wish to encrypt or decrypt a message?')
mode = input().lower()

In Python 2.x input use raw_input() instead of input().

Python 2.x:

• Read a string from standard input: raw_input()
• Read a string from standard input and then evaluate it: input().

Python 3.x:

• Read a string from standard input: input()
• Read a string from standard input and then evaluate it: eval(input()).

回答2:

input() evaluates the expression you type. Use raw_input() instead.