[shalabhc]

It does both. I can do some inference but definitely does type checking. Here's a Pycon talk from last year about pytype: https://youtu.be/IDm_YIQihhs

[bpicolo]

It needs severely more documentation, heh. Why would I use it over mypy, which appears to have a lot more community investment, thorough docs, and is somewhat official? It also doesn't support python3.6 so it doesn't know about format strings =/

[shalabhc]

pytype might work better in some cases, because it can do inference. But yes, it needs more docs.