import tkinter

import time

class Timer(tkinter.Label):

def __init__(self, master, format=lambda n: str(int(n)), limit=None, **options):

super().__init__(master, **options)

self.seconds = tkinter.DoubleVar()

def update(*args):

self["text"] = format(self.seconds.get())

self.seconds.trace('w', update)

if limit is not None:

def limiter(*args):

if self.seconds.get() >= limit:

self.seconds.set(limit)

self.stop()

self.seconds.trace('w', limiter)

self.seconds.set(0)

self._startpoint = 0

self._offset = 0

self.running = False

self._cancel = None

def start(self):

if not self.running:

self.running = True

self._startpoint = time.time()

self._run()

def stop(self):

if self.running:

self.running = False

if self._cancel is not None:

self.after_cancel(self._cancel)

self._cancel = None

self._offset = self._calculate_time()

def flip_state(self):

if self.running:

self.stop()

else:

self.start()

def reset(self):

if self.running:

self._startpoint = time.time()

else:

self._startpoint = None

self._offset = 0

self.seconds.set(0)

def _run(self):

self.seconds.set(self._calculate_time())

if self.running:

# traces on seconds (such as limit) can change this

self._cancel = self.after(100, self._run)

def _calculate_time(self):

return time.time() - self._startpoint + self._offset

if __name__ == '__main__':

root = tkinter.Tk()

def minutes_seconds(seconds):

minutes = int(seconds/60)

sec = int(seconds%60)

if sec < 10:

sec = '0'+str(sec)

return "Elapsed - {}:{}".format(minutes, sec)

timer = Timer(root, minutes_seconds)

timer.grid()

timer.bind("<Button-1>", lambda e: timer.flip_state())

timer.bind("<Button-3>", lambda e: timer.reset())

root.mainloop()