python
import toga
class MyFirstApp(toga.App):
def startup(self):
main_box = toga.Box()
main_box.add(label)
button.on_press = self.button_handler
main_box.add(button)
self.main_window = toga.MainWindow(title=self.name)
self.main_window.content = main_box
self.main_window.show()
def button_handler(self, widget):
label = widget.parent.children[0]
if __name__ == '__main__':
app.main_loop()
