Button' object has no attribute python callback

Question

I want to have the callback function for the btn1 to change the player1.center_y and to interact with my program in general(changing values in the Gameclass).

However I get the error

' Button' object has no attribute 'player1 ' when the button is clicked. Is it because the instance class in wrong or something?.I am kind of new to OOP.

here is the relevant code:

class Gameclass(Widget):
    def on_touch_move(self, touch):
        if touch.x < self.width / 3:
            self.player1.center_y = touch.y
        if touch.x > self.width - self.width / 3:
            self.player2.center_y = touch.y

    def callback(self):
            self.player1.center_y = 22
            self.player2.center_y = 250

btn1 = Button(text='click me')
btn1.bind(on_press=Gameclass.callback)

Answer 1

My comment may be difficult to understand, so here is an example:

class Gameclass(Widget):
    def on_touch_move(self, touch):
        if touch.x < self.width / 3:
            self.player1.center_y = touch.y
        if touch.x > self.width - self.width / 3:
            self.player2.center_y = touch.y

    def callback(self, btn_instance):
            self.player1.center_y = 22
            self.player2.center_y = 250

btn1 = Button(text='click me')
gc = Gameclass()
btn1.bind(on_press=gc.callback)

Note that you probably create an instance of Gameclass somewhere else in your code, and that instance should be used.