Tk_stopwatch.py

# Tk_stopwatch.py

from Tkinter import *
import datetime

def update_timeText():
    dtx = datetime.datetime.utcnow() - timeText.prev
    timeText.prev = datetime.datetime.utcnow()
    if state:
        timeText.curr += dtx
        dt = timeText.curr
        s = dt.seconds
        ms = dt.microseconds / 10000
        m = s / 60

        timeString = pattern.format(m,s%60,ms)
        if m > 99:
            timeString = '99:99:99'

        if not timeText.onSplit:
            timeText.configure(text=timeString, fg='green')

    root.after(1, update_timeText)

def start_x_pause():
    global state
    if timeText.onSplit:
        timeText.onSplit = 0
        update_timeText()
    state = (1,0)[state]
    if timeText.curr == zero:
        timeText.prev = datetime.datetime.utcnow()
    timeText.configure(fg=('red'))

def reset():
    timeText.configure(text='00:00:00', fg='black')
    timeText.prev = datetime.datetime.utcnow()
    timeText.curr = zero
    timeText.onSplit = 0

def split():
    if state:
        timeText.configure(fg='blue')
        timeText.onSplit = (1,0)[timeText.onSplit]

def exist():
    root.destroy()

state = 0

root = Tk()
root.wm_title('Tkinter Stopwatch')

zero = datetime.datetime.now() - datetime.datetime.now()

pattern = '{0:02d}:{1:02d}:{2:02d}'

timeText = Label(root, font=("Helvetica", 150))
timeText.pack()

start_x_pauseButton = Button(root, text='Start/Pause', command=start_x_pause)
start_x_pauseButton.pack(side=LEFT)

splitButton = Button(root, text='Split', command=split)
splitButton.pack(side=LEFT)

resetButton = Button(root, text='Reset', command=reset)
resetButton.pack(side=LEFT)

quitButton = Button(root, text='Quit', command=exist)
quitButton.pack(side=LEFT)

reset()
update_timeText()
root.mainloop()