python - 为什么这个程序中索引会越界？

Question

出于某种原因，我在运行此命令并输入 26 个字母 key 时在 python 2.7 中遇到错误。它说列表索引超出范围。任何帮助将不胜感激。谢谢! (而且我知道我可以使用加密器循环)

#-------------------------#
#     Code Translator     #
#-------------------------#

message = ''
messagearray = []
user = ''
encrypted = []
decrypted = []
keystring = ''
alphabet = ['a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z']
dataset = []
keyarray = []

def encrypter():
    keystring = raw_input("Please paste key: ")
    message = raw_input("Message to Encrypt: ")

    for char in message:
        if char == alphabet[0]:
            messagearray.append(keyarray[0])
        elif char == alphabet[1]:
            messagearray.append(keyarray[1])
        elif char == alphabet[2]:
            messagearray.append(keyarray[2])
        elif char == alphabet[3]:
            messagearray.append(keyarray[3])
        elif char == alphabet[4]:
            messagearray.append(keyarray[4])
        elif char == alphabet[5]:
            messagearray.append(keyarray[5])
        elif char == alphabet[6]:
            messagearray.append(keyarray[6])
        elif char == alphabet[7]:
            messagearray.append(keyarray[7])
        elif char == alphabet[8]:
            messagearray.append(keyarray[8])
        elif char == alphabet[9]:
            messagearray.append(keyarray[9])
        elif char == alphabet[10]:
            messagearray.append(keyarray[10])
        elif char == alphabet[11]:
            messagearray.append(keyarray[11])
        elif char == alphabet[12]:
            messagearray.append(keyarray[12])
        elif char == alphabet[13]:
            messagearray.append(keyarray[13])
        elif char == alphabet[14]:
            messagearray.append(keyarray[14])
        elif char == alphabet[15]:
            messagearray.append(keyarray[15])
        elif char == alphabet[16]:
            messagearray.append(keyarray[16])
        elif char == alphabet[17]:
            messagearray.append(keyarray[17])
        elif char == alphabet[18]:
            messagearray.append(keyarray[18])
        elif char == alphabet[19]:
            messagearray.append(keyarray[19])
        elif char == alphabet[20]:
            messagearray.append(keyarray[20])
        elif char == alphabet[21]:
            messagearray.append(keyarray[21])
        elif char == alphabet[22]:
            messagearray.append(keyarray[22])
        elif char == alphabet[23]:
            messagearray.append(keyarray[23])
        elif char == alphabet[24]:
            messagearray.append(keyarray[24])
        elif char == alphabet[25]:
            messagearray.append(keyarray[25])

    print ''.join(messagearray) 




def decrypter():
    keystring = raw_input("Please paste key: ")
    message = raw_input("Message to Decrypt: ")





def outputM():
    print decrypted

def userChoice():
    user = raw_input("Encrypt or Decrypt?")
    if user.upper() == "ENCRYPT":
        encrypter()
    elif user.upper() == "DECRYPT":
        decrypter()
    else:
        print "Please enter a valid command."
        userChoice()

for char in keystring:
    keyarray.append(char)

userChoice()

这是我得到的完整回溯:

Traceback (most recent call last):
  File "translate.py", line 102, in <module>
    userChoice()
  File "translate.py", line 92, in userChoice
    encrypter()
  File "translate.py", line 43, in encrypter
    messagearray.append(keyarray[11])
IndexError: list index out of range

Answer 1

问题出在这里:

for char in keystring:
    keyarray.append(char)

keystring 为空，因此 keyarray 也将保持为空。为了不出现 IndexError，您需要一个与字母表一样长的键字符串(因为基本上您只是替换字符)