Python - 消息加密返回`NoneType`錯誤

Question

我想使用偶數和奇數的定義來加密我的消息。 功能def swap_letters(message)是我使用的是什麼：

• 我遍歷的奇怪的名單，甚至與'「的消息=消息+‘X’」'信;
• 然後，我給"for counter in range(0, int(len(message)/2)): ...添加下一個奇怪的字母給最後的消息;
• 最後，我在我的new_message通過加入letter_1添加使用"letter_1.append(even_letters[counter])...

我作出最後的消息下一個偶數字母，然後返回它

我做什麼錯誤，我應該怎麼解決這個問題代碼讓它正確運行？

import tkinter as Tk 
from tkinter import messagebox, simpledialog, Tk 

def is_even(number): 
    return number % 2 == 0 

def get_even_letters(message): 
    even_letters = [] 
    for counter in range(0, len(message)): 
     if is_even(counter): 
      even_letters.append(message[counter]) 


def get_odd_letters(message): 
    odd_letters = [] 
    for counter in range(0, len(message)): 
     if not is_even(counter): 
      odd_letters.append(message[counter]) 
    return odd_letters 

def swap_letters(message): 
    letter_1 = [] 
    if not is_even(len(message)): 
     message = message + 'x' 
    even_letters = get_even_letters(message) 
    odd_letters = get_odd_letters(message) 
    for counter in range(0, int(len(message)/2)): 
     letter_1.append(odd_letters[counter]) 
     letter_1.append(even_letters[counter]) 
    new_message = ''.join(letter_1) 
    return new_message 

def get_message(): 
    message = simpledialog.askstring('Message', 'Enter the secret here: ') 
    return message 

def get_task(): 
    task = simpledialog.askstring('Task', 'Do you want to encrypt or decrypt?') 
    return task 

root = Tk() 

while True: 
    task = get_task() 
    if task == 'encrypt': 
     message = get_message() 
     encrypted = swap_letters(message) 
     messagebox.showinfo('Ciphertext of the secret message is:', encrypted) 
    elif task == 'decrypt': 
     message = get_message() 
     decrypted = swap_letters(message) 
     messagebox.showinfo('Plaintext of the secret message is:', decrypted) 
    else: 
     break 
root.mainloop() 

這是錯誤我得到：

Traceback (most recent call last): 
    File "T:\Sublime Text 3\shhhhh.py", line 47, in <module> 
    encrypted = swap_letters(message) 
    File "T:\Sublime Text 3\shhhhh.py", line 29, in swap_letters 
    letter_1.append(even_letters[counter]) 

TypeError: 'NoneType' object is not subscriptable 
[Finished in 21.2s with exit code 1] 
[shell_cmd: python -u "T:\Sublime Text 3\shhhhh.py"] 
[dir: T:\Sublime Text 3] 
[path: C:\Program Files (x86)\Python36-32\Scripts\;C:\Program Files `(x86)\Python36-32\;C:\WINDOWS\system32;C:\WINDOWS;C:\WINDOWS\System32\Wbem;C:\WINDOWS\System32\WindowsPowerShell\v1.0\;C:\Program Files (x86)\NVIDIA Corporation\PhysX\Common;C:\Program Files\dotnet\;C:\Program Files\Microsoft SQL Server\130\Tools\Binn\;C:\Program Files (x86)\Xoreax\IncrediBuild;C:\Users\mwliv\AppData\Local\Microsoft\WindowsApps;]` 

Answer 1

你get_even_letters功能不明確返回任何東西，所以它含蓄地返回None，因而錯誤你以後看到。添加return語句應解決該問題：

def get_even_letters(message): 
    even_letters = [] 
    for counter in range(0, len(message)): 
     if is_even(counter): 
      even_letters.append(message[counter]) 

    return even_letters # Here! 

Answer 2

只需修改類似下面的代碼： -

for counter in range(0, int(len(message)/2)): 
    # You need to verify whether values are None type or not before calling append 
    if(odd_letters != None): 
     letter_1.append(odd_letters[counter]) 
    if(even_letters != None): 
     letter_1.append(even_letters[counter])