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.