Stop watch implemented with kivy.clock.Clock

Kivy_stop_watch

from kivy.app import App
from kivy.lang import Builder
from kivy.properties import NumericProperty
from kivy.uix.boxlayout import BoxLayout
from kivy.clock import Clock
 
Builder.load_string('''
<MainWidget>:
    BoxLayout:
        orientation: 'vertical'
        Button:
            text: 'start'
            on_press: root.start()
            # Choose an image and uncomment:
            #background_down: 'button_pressed.png'
            #background_normal: 'button_normal.png'
            #color: [0, 0, 0, 1]
        Button:
            text: 'stop'
            on_press: root.stop()
            # If you have a favourite font, you can use that:
            #font_name: 'font_name.ttf'
            #font_size: '22dp'
        Button:
            text: 'Set to 0'
            on_press: root.number = 0
    Label:
        text: str(root.number)
        text_size: self.size
        halign: 'center'
        valign: 'middle'
''')
 
 
class MainWidget(BoxLayout):
    number = NumericProperty()
    def __init__(self, **kwargs):
        super(MainWidget, self).__init__(**kwargs)
        Clock.schedule_interval(self.increment_time, .1)
        self.increment_time(0)
        
    def increment_time(self, interval):
        self.number += .1
        
    def start(self): 
        Clock.unschedule(self.increment_time)
        Clock.schedule_interval(self.increment_time, .1)
        
    def stop(self):
        Clock.unschedule(self.increment_time)
         
class ExampleApp(App):
    def build(self):
        return MainWidget()
 
ExampleApp().run()