Pythonic Refactoring: Protecting Your Users From Change

So you’ve released a library! Now you need to maintain it. You want to add features, restructure the code, fix bugs, and maybe improve the library’s usability. Your users just want their code to carry on working. That’s okay!

This talk will cover techniques in both code and project management to allow you to keep your code moving forwards without breaking your users’ code. It is aimed at developers with a little experience of writing libraries in Python, and will cover some intermediate subjects like function decorators and magic methods.

Refactoring in Python is a mixed bag - on the one hand you have powerful tools like the @property decorator, __dunder__ methods, and even metaclasses. On the other hand, because Python code has no concept of private or protected like some other languages, it can be difficult to know what your public interface even is.

I’ll talk about how to identify your public interface, and make that clear to your users (cough documentation cough). I’ll cover how to structure your tests so you know when you’ve broken your public interface. I’ll discuss how to use some of Python’s language features to trick your users into thinking your code hasn’t changed at all (except for those brilliant new features you’ve just added!). And finally, I’ll cover how you know it’s time to break backwards compatibility and how to break it to your users.