在 Turtle 中使用 screen.onclick() 和返回多个值的函数 [英] Using screen.onclick() in Turtle with a function that returns multiple values

问题描述

我试图将用户鼠标点击的坐标用作另一个函数的 x 和 y.当第二个函数运行时，它返回两个值(不是 x 和 y).

I am trying to use the coordinates from a user's mouse click as the x and y for another function. When that second function runs, it returns two values (not x and y).

但是当我运行 onclick 方法时，我得到TypeError: cannot unpack non-iterable NoneType object"；在我点击任何东西之前.

But when I run the onclick method, I get "TypeError: cannot unpack non-iterable NoneType object" before I even click anything.

def on_click(x, y):
        t = turtle.Turtle()
        screen = turtle.Screen()
        t.penup()
        t.goto(x, y)

        #do stuff part 1
        #do stuff part 2

        return value1, value2

def main():
        t = turtle.Turtle()
        screen = turtle.Screen()
        value1, value2 = screen.onclick(on_click)

        #do other stuff with value1 and value2

main()

我是否错误地使用了海龟的 onclick 函数?或者我的龟屏设置错误?

Am I using the turtle onclick function incorrectly? Or perhaps setting up my turtle screen wrong?

否则，如果我在使用 onclick 时无法返回多个值，有什么办法可以让这两个值返回到我的主函数中?

Else, if I can't return multiple values while using onclick, what would be a work around for getting those two values back into my main function?

任何帮助将不胜感激！

推荐答案

此语法表明您没有正确考虑事件处理程序:

This syntax indicates you are nor thinking about event handlers correctly:

value1, value2 = screen.onclick(on_click)

screen.onclick() 函数不返回任何东西(即None)和你的on_click()code> 函数不能返回任何东西(即None).此时您没有在代码中调用 on_click() ，将来如果/当发生点击时会调用它，因此返回值不适用.(调用者不能使用它们.)

The screen.onclick() function doesn't return anything (i.e. None) and your on_click() function can't return anything (i.e. None). You are not calling on_click() at this point in the code, it will be called in the future if/when a click occurs, so returning values doesn't apply. (The caller can't use them.)

您有一些选择:您可以将 (value1, value2) 放入 global 以供其他代码访问；您可以将其传递给另一个函数调用.但是你不能返回它.在结构上，您的代码可能如下所示:

You've got some choices: you can put (value1, value2) into a global for some other code to access; you can pass it to another function call. But you can't return it. Structurally, your code might look like:

from turtle import Screen, Turtle

def on_click(x, y):
    screen.onclick(None)  # disable handler inside handler

    turtle.goto(x, y)

    # do stuff part 1
    # do stuff part 2

    some_other_function(value1, value2)

    screen.onclick(on_click)  # reenable handler

def some_other_function(v1, v2):
    #  do other stuff with value1 and value2
    pass

screen = Screen()

turtle = Turtle()
turtle.penup()

screen.onclick(on_click)

screen.mainloop()

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