Tkinter Button disable does not work - python-2.7

Question

Hi i am trying to disable a button , so that the command event does not work for some time .How can i make the button disabled for some time and then later reenable it , to get the callback function .
#! /usr/bin/python
from Tkinter import *
import Tkinter as tk
import time
class MyFrame(Frame):
def __init__(self, master):
Frame.__init__(self, master)
self.b1 = Button(self, text="Press Me!",command = self.callback)
self.count=0
self.but_flag=0
self.b1.grid()
def callback(self):
self.b1['state'] = DISABLED
for k in range(5):
time.sleep(1)
print k
self.b1['state'] = NORMAL
mainw = Tk()
mainw.f = MyFrame(mainw)
mainw.f.grid()
mainw.mainloop()

Answer 1

The problem is that the sleep in your callback function is blocking the UI from refreshing. Instead of using sleep, you could schedule the re-enabling of the button using after.
def callback(self):
self.b1['state'] = DISABLED
self.after(3000, self.enable)
def enable(self):
self.b1['state'] = NORMAL
But if you do any long-running task in callback, this will still freeze the UI.
Another alternative would be to create a worker thread for doing the actual work. This way, the UI thread is not blocked and the UI will be updated and the button deactivated/activated.
def callback(self):
threading.Thread(target=self.do_actual_work).start()
def do_actual_work(self):
self.b1['state'] = DISABLED
for i in range(5):
print i
time.sleep(1)
self.b1['state'] = NORMAL
Of course, you could also just add self.b1.update() after the disabling line to update the Button widget to its disabled state, but this will still leave the UI frozen until the method is finished.