Cog is a way that you can make a text file like a read me dot MD and put little bits of Python in the middle. It's just like ginger, but instead of being HTML, you want it to be text or something. So for instance, I use this in the coverage.py docs. There's a database schema for the SQLite data file that coverage.py writes which Cog then splat into the restructure text file so there's one source of truth.