Scala doesn't/cannot use Hindley-Milner, I doubt it could be any easier to apply it to Python. (Clojure core.typed doesn't use hindley milner either afaik. There've been experiments on that front though)

Also, type inference doesn't mix very well with dynamic types ("dynamic is viral", or similar things, I've briefly skimmed this post and I think it makes the point: http://ericlippert.com/2012/11/09/dynamic-contagion-part-two... )