I'm really not anfan of linking libpython if I can avoid it. More wheels to build and then its limited to cpython. Cffi is plenty fast.
Which method do you find easiest (read: least developer time) for using large rust codebases from Python?
CFFI works quite well. I will probably make a post on my blog later with some ideas on how to do it.
Not only does it work well, it is portable across nearly all Pythons you would want to use, CPython and PyPy.
Can you import that as a lib in Python to work in reverse? It seems to be a different use-case otherwise - using a Python library from Rust vs optimizing a hotspot within Python.