python - Launch TkInter GUI using Watchdog event

Question

I'm using python package Watchdog to monitor a file for changes, and want to launch a GUI when the file is modified. Currently when I'm initiating the GUI inside the custom handler, the GUI window freezes. Here's a rough idea of what my code looks like:

class MyHandler(FileSystemEventHandler):
   def on_modified(self, event):
        window = tk.Tk()
        window.title("app")
        window.mainloop()

if __name__ == "__main__":
   path = sys.argv[1] if len(sys.argv) > 1 else '.'
   event_handler = MyHandler()
   observer = Observer()
   observer.schedule(event_handler, path)
   observer.start()
   try:
      while True:
         time.sleep(1)
   except KeyboardInterrupt:
      observer.stop()
   observer.join()

Any help on this would be greatly appreciated! Thanks!