Kivy call SELF method from another class

Question

In this very simple kivy python program I try to change text label from Window2 class using method in Window1 class. When I call in Window2 for Window1 method, method is launched, but self.ids .... line is not done.

Any idea what must be changed to make the self.ids.label1.text = "DONE" work?

python file

from kivy.uix.boxlayout import BoxLayout


class ParentWindow(BoxLayout):
    pass


class Window1(BoxLayout):

    def update(self):
        print("This print works, but next line not ...")
        self.ids.label1.text = "DONE"


class Window2(BoxLayout):

    def try_change(self):
        Window1().update()


class MyProgramApp(App):
    def build(self):
        return ParentWindow()


MyProgramApp().run()

kivy file

<ParentWindow>:
    Window1:
    Window2:

<Window1>:
    orientation: "vertical"
    Label:
        id: label1
        text: "Try to change me"
    Button:
        text: "Works fine from self class"
        on_press: root.update()

<Window2>:
    Button:
        text: "Lets try"
        on_press: root.try_change()

Answer 1

I have found solution:

.py

from kivy.app import App
from kivy.uix.boxlayout import BoxLayout


class ParentWindow(BoxLayout):
    pass


class Window1(BoxLayout):

    def update(self):
        print("This print work, but next line not ...")
        self.ids.label1.text = "DONE"


class Window2(BoxLayout):

    def try_change(self):
        self.parent.ids.win1.update()


class MyProgramApp(App):
    def build(self):
        return ParentWindow()


MyProgramApp().run()

.kv

<ParentWindow>:
    Window1:
        id: win1
    Window2:


<Window1>:
    orientation: "vertical"
    Label:
        id: label1
        text: "Try to change me"
    Button:
        text: "Works fine from self class"
        on_press: root.update()

<Window2>:
    Button:
        text: "Lets try"
        on_press: root.try_change()