main.py

from kivy.app import *
from kivy.uix.widget import Widget
from kivy.uix.button import Button
 
class MyHomeScreen(Widget):
    pass
       
class ButtonTest(Button):
    pass
               
class MyAlarmApp(App):
    def build(self):
        pass
               
if __name__ == '__main__':
    MyAlarmApp().run()

myalarm.kv

#:kivy 1.0.9

MyHomeScreen:

<MyHomeScreen>:
	BoxLayout:
		size: 800, 600
		#orientation:"vertical"
		spacing: 10
		on_size: print 'box_layout_size', self.size
		ButtonTest:

<ButtonTest>:
	text: "1"
	size_hint: (1, 1)
	on_size: print 'button interior size', self.size