問題描述

按下按鈕調用函數時，我無法將參數傳遞給函數.用 kivy 語言可以這樣做:

I am having trouble passing parameters to function when calling it with button press. One could do it like this in kivy language:

Button: 
   on_press: root.my_function('btn1')

但我想用 python 來做，因為我想用循環創建更多的按鈕.目前我在 python 中這樣調用我的函數:

but I would like to do it in python, as I would like to create a larger number of buttons with a loop. Currently I call my function in python like this:

Button(on_press=self.my_function)

但正如我所說，如果我嘗試像這樣將參數傳遞給函數，我會得到一個AssertionError: None is not callable"，如下所示:

but as I said, if I try to pass a parameter to the function like this, I get an 'AssertionError: None is not callable', like this:

Button(on_press=self.my_function('btn1'))

推薦答案

Button(on_press=self.my_function)

這是傳遞函數作為參數.

Button(on_press=self.my_function('btn1'))

這是調用函數并將返回值作為參數傳遞給on_press.由于返回值為 None，因此您會收到錯誤消息.

This is calling the function and passing the returned value as the argument to on_press. Since the returned value is None, you get your error.

您需要傳遞一個調用普通函數并自動傳遞參數的新函數.總的來說，使用 functools.partial 比較方便:

You instead need to pass a new function that calls your normal function and automatically passes the argument. In general, it's convenient to use functools.partial:

from functools import partial
Button(on_press=partial(self.my_function, 'btn1'))

您還可以使用 lambda 函數:

You can also use a lambda function:

Button(on_press=lambda *args: self.my_function('btn1', *args))

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