Starting a thread

This recipe will show us how to start a thread. It will also demonstrate why threads are necessary to keep our GUI responsive during long-running tasks.

Getting ready

Let's first see what happens when we call a function or method of our GUI that has some sleep associated with it without using threads.

Note

We are using a sleep here to simulate a real-world application that might have to wait for a web server or database to respond or a large file transfer or complex computation to complete its task.

The sleep is a very realistic place-holder and shows the principle involved.

Adding a loop into our button callback method with some sleep time results in our GUI becoming unresponsive and, when we try to close the GUI, things get even worse.

# Button callback
def clickMe(self):
  self.action.configure(text='Hello ' + self.name.get())
  # Non-threaded code with sleep freezes the GUI
  for idx in range(10):
    sleep(5)
    self.scr.insert(tk.INSERT, str(idx) + '\n')

If we wait long...