#! /usr/bin/env python
from Tkinter import *
from time import *

class clock:
    def __init__(self,master):
        self.starttime=0 
        self.widget=Button(master, text="0:0",
                           font=("Courier",50,"bold"),
                           relief=FLAT,command=self.reset)
        self.widget.pack()

    def idle(self):
        thistime = int(time()-self.starttime)
        self.widget.config(text=str(thistime/60)+":"+str(thistime%60))
        self.widget.after(1000, self.idle)

    def reset(self):
        if not self.starttime:
            self.widget.after_idle(self.idle)
        self.starttime=time()

win = Tk()
win.title("ticktock")
slider = clock(win)
win.mainloop()