An example of OOD design for python beginners and children.
There are only two files here, "good.py" and "bad.py". Obviously it is better to begin with the "bad.py" file, to see what we're trying to improve. To run the files, just type "python good.py", for example. Some IDEs may not be able to clear the screen using the cls or clear command. It does work good in the Windows cmd window, or (if you replace the "cls" to "clear" in both files) in Linux terminals.
There's also a class diagram, which can help understand the structure and the dependencies of the code. Open it in http://draw.io/.
Hope this is helpful.