I was a bit nervous about this trend when it started picking up because I care about Pyodide (Python running via WebAssembly) and libraries that use PyO3 might not work in Pyodide.
Thankfully that's now been mostly solved - you can compile and publish WASM builds of Rust or C extensions on PyPI now and a Pyodide can then use them.
I'm kind of surprised to hear that was a concern because my perception is that PyO3 is more analogous to wrapping native C code in Python libraries (which is pretty well established since long before either Rust or WASM), and Pyodide seems more like something for use in browsers rather on the server-side. When I looked into this earlier this year, trying to run Python via WASM on the server side with Pyodide had a bunch of hoops I needed to jump through, and it ended up being a lot simpler to use a build of Python from one of the core Python contributors that directly targeted WASM.
But does it work everywhere Python works? My main issue with this Rust move has always been compatibility. Python can be embedded and ran in a heck of a lot of places. What's the story when libraries that I may want to depend on are actually implemented in Rust and my target doesn't/can't handle the toolchain and there's no build target?
It won't work in those cases. Do you have explicit examples? I suspect this won't come up much as Rust has, IME, much broader target support. (Including platforms without a GPOS)
This is a nice party trick! I use it to provide easy installation of software that is written in rust, but is primarily used by Python users. (e.g.: Biology tools) They can do `pip install <name>`, since some people prefer this over downloading executables/installers. Bonus: Maturin/PyO3 can build "manylinux" binaries automatically, which helps with the Linux ABI diaspora.
Thankfully that's now been mostly solved - you can compile and publish WASM builds of Rust or C extensions on PyPI now and a Pyodide can then use them.
Here's the WASM build of the Rust-including Pydantic-core package for example: https://pypi.org/project/pydantic_core/#pydantic_core-2.49.0...
ai; dr, sorry