(For those living in the python + typing world, I'd definitely recommend trying Microsoft's pyright as an alternative to mypy. In my experience, it is substantially faster and produces higher quality error messages. It does not support mypy plugins, so -- for instance -- Django ORM dynamism isn't well captured. But I've found that the Django plugin for mypy is still pretty young; when used on a big codebase, it both slows down type checking considerably and regularly produces spurious errors.

Random: as someone who makes heavy use of both Python and Typescript, it pleases me to no end to see a great parser and ast for python implemented in typescript.)