size_hint and pos_hint demonstration

gistfile1.py

from kivy.app import App
from kivy.uix.button import Button
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.screenmanager import Screen


class TestScreen(Screen):
    def __init__(self, *args, **kwargs):
        super(TestScreen, self).__init__(*args, **kwargs)

        layout = BoxLayout(
            orientation='vertical',
            spacing=5,
            padding=10,
            size_hint_y=1 / 3.,
            pos_hint={'top': 1}
        )

        for i in range(1, 4):
            layout.add_widget(Button(text='Button %d' % i))

        self.add_widget(layout)

class TestApp(App):
    def build(self):
        return TestScreen()
 
if __name__ == '__main__':
    TestApp().run()