I like doing katas, particularly refactoring katas. I've been creating some small repositories for refactoring katas in Python3.
Refactoring katas are katas) where you're given some code that works (sometimes) and the goal is to make it readable, and sometimes, to add some features.
So one way to do them is by creating a golden test and/or creating unit tests where you can isolate features and then refactor away once you're confident you're not changing their behaviour.
So, here is the list of the katas I've gotten so far, I'm putting my own solutions in branches so I don't pollute master with them.
Note: My solutions are not necessarily the best!