python gtk async

main.py

#!/usr/bin/env python3
import gi
# gtk import
gi.require_version("Gtk", "3.0")
from gi.repository import Gtk, GLib

# thread import
import threading

# for sleep
import time

# gui elements
w = Gtk.Window()
l = Gtk.Label()

# blocking function 
def count():
    num=0
    while True:
        # gtk related functions must run with GLib.idle_add
        GLib.idle_add(l.set_label, str(num))
        time.sleep(1)
        num=num+1

# thread create and start
thread = threading.Thread(target=count)
thread.daemon = True
thread.start()

# gui signals
w.connect("destroy", Gtk.main_quit)
w.add(l)
w.show_all()

# start
Gtk.main()