We've had mypy, the Python type checker, running in Travis-CI on lang/py for a little while. However, mypy doesn't actually check code unless it has type hints, so it has been doing very little. Now that we are only supporting Python 3.5 and up, we can add real type hints!
I'm excited about this, because I think it will really improve the Python implementation. There are a fair amount of Liskov violations and other places where type theory rules have been bent or broken in the Python implementation, so there will be places where we need to decide if we want to make an API breaking change, or ignore an inconsistency. If you want to see what mypy is able to check right now, you can install mypy and lxml and run mypy --html-report mypy-html and open mypy-html/index.html in your browser. If you can find the time to open a PR against AVRO-2921 and introduce type hints in a single module or test, please give it a shot. If the type checker finds a bug as a result, please report the bug. Happy Hinting!
