Pyrefly is not the first Python type-checking tool from Meta. Previously, the company delivered Pyre, written in OCaml. Pyre ...

Python type hints are used ahead of time, by the type-checking system; for instance, in your editor or IDE. In other words, Python’s type hints are for the developer , not the runtime.

But as Python (and other dynamic languages) have been making inroads into large companies, I've become increasingly convinced that there's something to be said for type checking. In particular, the ...