PyO3 is great. I have been using it to rewrite some slow python code. My only complaint is that documentation is a bit rough. For someone who understands python, but not rust, there was a pretty big hill to climb to understand type conversions.

There are also things I am still struggling with. For example, there is a rust function I want to repeatedly call from python, that takes in a large unchanging python array. How can I pass the array from python to rust only once, i.e do the type conversion just once, so I don't have to pay that cost repeatedly.