I'm interested to find out how you made the decision to use Rust for this project. It seems like it would have been much simpler to use Python directly. Were you trying to learn about the Rust-Python FFI? Was there a performance concern with a native-Python version?

Performance was a slight concern, but more important was correctness.

This used the widely used and very stable toml library from rust.

It started because I tried the most popular toml library for python and found significant bugs and poor code quality. Some other libraries had fewer bugs but were very slow. Then I wondered how hard it would be to use the rust library from python via pyo3, and here we are.