How to build a Tkinter application using an object oriented approach

In a previous tutorial we saw the basic concepts behind the usage of Tkinter, a library used to create graphical user interfaces with Python. In this article we see how to create a complete although simple application. In the process, we learn how to use threads to handle long running tasks without blocking the interface, how to organize a Tkinter application using an object oriented approach, and how to use Tkinter protocols.