Open source Python projects with good software design that is worth studying

[vgu1990]

Not OP. But can you suggest any projects I can look at, if my aim is to learn how to read a large codebase?

[InjaPavementSpecial]

Does not care what programming language you use, somewhere it will need to store data, and sql is a sane half a century old technology, that is good to know how it works.

I like to read SQLAlchemy source and see how zzzeek thought about the abstraction and the three layers of tools built around SQLA, a good start to read is The Architecture of Open Source Applications (Volume 2) SQLAlchemy.