I would suggest starting with reading a spec for your favorite language. I got a lot of value from spending time with the Ecmascript (JS) spec, as well as the P

I would suggest starting with reading a spec for your favorite language. I got a lot of value from spending time with the Ecmascript (JS) spec, as well as the Postgres manual. Take something like Generators that may be less familiar to you, then plunk those expressions into sourcegraph or github search and find them used in real codebases. Try to understand why the developers chose to use a generator instead of another pattern. I think reading code itself is only valuable when you need to explore a specific domain. Trying to extract coding patterns from an unfamiliar domain very difficult; it comes with unseeable assumptions.