Mypy, Pytype, Pyright, and Pyre can help you keep your type-hinted Python code bug-free. Let’s see what each of these useful tools has to offer.

Learn how to use Python’s optional type-hinting syntax to create cleaner and more useful code.

The pip3 reflects that I'm using Python 3, rather than Python 2. And the -U option indicates that I'd like to upgrade my installation of mypy, if the package has been updated since I last installed it ...