stopwatch.py

#!/usr/bin/python2

import pyglet
from pyglet.window import key
import time

running = False
begin, now, total = 0, 0, 0
size = (320, 240)

window = pyglet.window.Window(size[0], size[1], caption="Stopwatch", 
                              visible=False)
label = pyglet.text.Label('00:00:00:00', font_size=36,
                          x=window.width/2, y=window.height/2,
                          anchor_x='center', anchor_y='center')
window.set_visible()

@window.event
def on_key_release(symbol, modifiers):
    global now, begin, running, total
    if symbol == key.SPACE:
        if not running:
            running = True
            begin = time.time()
        else:
            running = False
            now = time.time()
            total += now - begin
    if symbol == key.BACKSPACE:
        total = 0
        begin = time.time()
        running = False

@window.event
def on_draw():
    window.clear()
    label.draw()

def get_millis(timestamp):
    millis = str(timestamp - int(timestamp))[2:4]
    if millis == "":
        return "00"
    else:
        return millis

def update_time(dt):
    global now, begin, total
    if running:
        now = time.time()
        label.text = time.strftime("%H:%M:%S:", time.gmtime(now - begin + total)) + get_millis(now - begin + total)
    else:
        label.text = time.strftime("%H:%M:%S:", time.gmtime(total)) + get_millis(total)

pyglet.clock.schedule_interval(update_time, 0.01)
pyglet.app.run()