This frustrated me to the core. Stopped following up somewhere in the middle. Are these used often?

The first comment I will say-- if you don't quite follow what Kenneth is doing with subclassing built-ins, that's ok. This is "advanced objects" material. Don't let it stop you from moving on in other areas of Python that excite and interest you. You won't do much complex subclassing tasks in the real world as there are many ways to do something correctly (and clearly).

You will, however, always be using objects some you'll write from scratch, most will come from third-party or standard libraries. Some of these you will use directly or subclass into your own objects. So basic object-oriented-Python is fundamental -- some of the advanced stuff, not so much.