Comment by gpshead

Nope. Our pytype project started before Mypy even existed. It was inspired first by https://developers.google.com/closure/compiler/'s success, and soon after inspired by TypeScript being released by Microsoft. MyPy came on the scene later in the same year we has started to work on early (unsuccessful) versions PyType. We didn't release pytype until ~2015 and didn't focus on making it usable in the OSS world until the last couple of years.

Pytype started with larger goals: It focused on static analysis and type inference; much more so than any of the other Python type checkers today do.

PyType, like MyPy, is also capable of analyzing Python 2.7 code because existing codebases have a ton of that and understanding types can help when porting it to 3. A couple years from now will anyone care? We hope not!

Performance is a problem for dynamic language type analyzers. Particularly so for Python where CPython is slow yet analyzers want to be self hosted in the language they're written to analyze. Very interesting, though not wholly surprising, to see Pyre and Pyright choose to implement in other faster languages. MyPy also has MyPyC internally which is doing a very Cython-esque translation of some of their performance hot spots into CPython API C code for a speedup.

Interesting times.