Python now offers static types! Companies like Dropbox and Facebook, and open-source projects like Zulip, use static types (with PEP 484 and mypy) to make Python more productive and fun to work with — in existing codebases from 40k lines to 4 million, in Python 2 and 3, and while preserving the conciseness and flexibility that make Python a great language in the first place. I’ll describe how.