kv 26 embeded boxlayout

#embededlayout.py

from kivy.app import App

from kivy.uix.widget import Widget

class Embedlayout(Widget):

    pass

class EmbedlayoutApp(App):

    pass

EmbedlayoutApp().run()

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#embededlayout.kv

Embedlayout:

    BoxLayout:

        size: root.width, root.height

        Button:

            text: "A"

            size_hint: .5, .5

            pos_hint: {"center_y": .5}

        BoxLayout:

            orientation: "vertical"

            spacing: "10dp"

            Button:

                text: "B1"

            Button:

                text: "B2"

            Button:

                text: "B3"

        Label:

            text: "C"

reference:

https://www.youtube.com/watch?v=l8Imtec4ReQ&t=529s