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> It's a consequence of Python never having been designed as a language with a static type system Is it? Mypy is semi-official and has Guido as a contributor.

> It's a consequence of Python never having been designed as a language with a static type system Is it? Mypy is semi-official and has Guido as a contributor. It also predates both pyright and pyre by many years. Honestly I find it somewhat sad that huge tech companies create their own instead of contributing to an existing and popular implementation. But perhaps the internal versions predated Mypy by a lot.

Mehdi2277 4y ago
Pyright is pretty recent and started development years after mypy. But some of pyright's design goals (laziness for LSP) would have made it very difficult to do in mypy without a very large refactor/rewrite. Pyright is implemented in typescript for better LSP/vscode integration and performance. pytype (google's type checker) is only one I know that predates mypy for when it started development. Pyre's reason is interesting, https://github.com/facebook/pyre-check/issues/38 https://github.com/facebook/pyre-check/issues/38. Pyre is based off of Hack, facebook's php compiler. Facebook made pyre to re-use tooling/techniques from Hack on python. Secondary reason is performance. Pyre is done in OCaml and having same performance in type checker implemented within python is hard.