python - Sleep() stops threads -

i trying run script spawns couple of threads using root.after(). sleep() seems lock script. never sees flag being set second root.after().

from time import sleep tkinter import *  global flag flag = false  def settimer():     global flag      while(flag==false):         sleep(.1)     print('flag set')     return  def setflag():     global flag      flag=true     return  root=tk() print('start')  root.after(1,settimer()) root.after(100,setflag())  print('done') 

after not start new thread, runs method inside event-loop of tk. while-loop block program.

if use after method must non-blocking operations, checking flag. if have background processes, use real threads. notice: must not alter gui inside these threads!

import tkinter tk time import sleep threading import thread, event  flag = event()  def worker():     while not flag.is_set():         sleep(.1)     print('flag set')  def set_flag():     flag.set()  root = tk.tk() print('start')  thread(target=worker).start() root.after(100, set_flag)  print('done') root.mainloop()