如何在for循环中使用return语句?

问题描述

因此，我正在开发一个聊天机器人，以解决不和谐的问题，现在正在开发一个可以用作待办事项列表的功能.我有一个命令可以将任务添加到列表中，并将它们存储在字典中.但是我的问题是以更易读的格式返回列表(请参见图片).

So I am working on a chat-bot for discord, and right now on a feature that would work as a todo-list. I have a command to add tasks to the list, where they are stored in a dict. However my problem is returning the list in a more readable format (see pictures).

def show_todo():
    for key, value in cal.items():
        print(value[0], key)

任务存储在名为cal的dict中.但是，为了使该机器人实际发送消息，我需要使用return语句，否则它将仅将其打印到控制台而不是实际的聊天中(请参阅图片).

The tasks are stored in a dict called cal. But in order for the bot to actually send the message I need to use a return statement, otherwise it'll just print it to the console and not to the actual chat (see pictures).

def show_todo():
    for key, value in cal.items():
        return(value[0], key)

这是我尝试解决的方法，但是由于我使用了return，因此for循环无法正常工作.

Here is how I tried to fix it, but since I used return the for-loop does not work properly.

那我该如何解决呢?如何使用return语句，以便将其打印到聊天记录中而不是控制台中?

So how do I fix this? How can I use a return statement so that it would print into the chat instead of the console?

推荐答案

即使循环尚未完成，在循环内使用return也会破坏循环并退出函数.

Using a return inside of a loop will break it and exit the function even if the iteration is still not finished.

例如:

def num():
    # Here there will be only one iteration
    # For number == 1 => 1 % 2 = 1
    # So, break the loop and return the number
    for number in range(1, 10):
        if number % 2:
            return number
>>> num()
1

在某些情况下，如果满足某些条件，我们需要中断循环.但是，在您当前的代码中，在完成循环之前先中断循环是无意的.

In some cases we need to break the loop if some conditions are met. However, in your current code, breaking the loop before finishing it is unintentional.

相反，您可以使用其他方法:

Instead of that, you can use a different approach:

def show_todo():
    # Create a generator
    for key, value in cal.items():
        yield value[0], key

您可以这样称呼它:

a = list(show_todo())  # or tuple(show_todo())

或者您可以遍历它:

for v, k in show_todo(): ...

将您的数据放入列表或其他容器中

将数据追加到列表中，然后在循环结束后返回:

Putting your data into a list or other container

Append your data to a list, then return it after the end of your loop:

def show_todo():
    my_list = []
    for key, value in cal.items():
        my_list.append((value[0], key))
    return my_list

或使用列表理解:

def show_todo():
    return [(value[0], key) for key, value in cal.items()]

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