Manually updating a million line code base is tedious. Thankfully syntax trees provide a safe and quick way to automatically apply repetitive transformations. Leveraging syntax tree based tooling (based on lib2to3), has been a critical component of Pinterest’s Python 3 upgrade strategy, and saved us countless hours of work. Learn how syntax trees work, how they are used to transform code, and how you can quickly write your own transformations. Slides can be found at: …