#: import Button kivy.uix.button.Button

<KivyStackLayout>:
    orientation: 'lr-tb'

    on_kv_post:
        [self.add_widget(
        Button(
        text=chr(i + 65),
        width=(i + 1) * 10,
        size_hint=(None, 0.2),
        on_press=self.on_button_pressed
        )
        )
        for i in range(10)]