Open Collective
Open Collective
Tests aren’t enough: Case study after adding type hints to urllib3
Published on October 18, 2021 by Seth Michael Larson


With your support we've completed a large part of our v2.0 milestone, adding type hints to urllib3. Thank you!

As a part of this project we wanted to share the journey, what we learned, and problems we encountered along the way as well as celebrate this accomplishment for the urllib3 project.

Since Python 3.5 was released in 2015 including PEP 484 and the typing module type hints have grown from a nice-to-have to an expectation for popular packages. To fulfill this expectation our team has committed to shipping type hints for the v2.0 milestone. What we didn’t realize is the amount of value we’d derive from this project in terms of code correctness.