pybind11 VS setuptools-rust

I'm investigating using C++ to build a REST server, and would love to know of people's experiences with Crow-- or whether they would recommend something else as a "medium-level" abstraction C++ web server. As background, I started off experimenting with Python/FastAPI, which is great, but there is too much friction to translate from pybind11-exported C++ objects to the format that FastAPI expects, and, of course, there are inherent performance limitations using Python, which could impact scaling up if the project were to be successful.

I have a C++ function computing a large tensor which I would like to return to Python as a NumPy array via pybind11.

This is based on the Google Ink Stroke Modeler C++ library, and using pybind11 to make it available on python.

pybind11 makes it easy to call C++ from Python if you want to mix.

If you've never used Pybind before these pybind tests[1] and this repo[2] have good examples you can crib to get started (in addition to the docs). Once you handle passing/returning/creating the main data types (list, tuple, dict, set, numpy array) the first time, then it's mostly smooth sailing.

Pybind offers a lot of functionality, but core "good parts" I've found useful are (a) use a numpy array in Python and pass it to a C++ method to work on, (b) pass your python data structure to pybind and then do work on it in C++ (some copy overhead), and (c) Make a class/struct in C++ and expose it to Python (so no copying overhead and you can create nice cache-aware structs, etc.).

[1] https://github.com/pybind/pybind11/blob/master/tests/test_py...

I have a python module for which the logic is written in C++ and I use pybind11 to expose the objects and functions to Python.

Reading from Python requires a wrapper, using pybind11 this is fairly done.

For Python specifically, In addition to using rust-cpython or PyO3, maturin makes it really comfortable to build, package, and publish Rust code into Python packages and, if your niche doesn't quite fit, there's setuptools-python which might do it.

Aside from the PyO3 and rust-cpython crates already mentioned, I'd suggest maturin as a way to integrate your build processes or possibly setuptools-rust.

Compiled modules for Python stuff (I'd recommend PyO3 but the last one I started was before that worked on stable Rust, so I used its progenitor, rust-cpython. See also maturin or setuptools-rust).

...but you will need to rename the generated library to match import conventions. setuptools-rust or Maturin can help with that.

Between pyodide, pyo3, rust-cpython, and rustpython, I think Pyo3 is the best way to drop in rust in a python project for a speed up, if that is your goal. Some of the demos show using python from rust, but to me the biggest feature is without a doubt compiling rust code to native python modules. I'm using it to speed up image manipulation backed by numpy arrays.

There’s a setuptools rust [0] extension package that can be used to hook the compilation of the rust into the wheel building or install from source. Maturin [1] seems to be regarded as the new and improved solution for this, but I found that it’s angled toward the using python from rust.

There’s also the rust numpy [2] package by the same org which is fantastic in that it lets you pass a numpy matrix to a native method written in rust and convert it to the rust equivalent data structure, perform whatever transformation you want (in parallel using rayon [3]), and return the array. When building for release, I was seeing speed ups of 100x over numpy on the most matrix mathable function imaginable, and numpy is no joke.

I think there is a lot of potential for these two ecosystems together. If there’s not a python package for something, there’s probably a rust crate.

If anyone is interested the python package that I'm building with some rust backend, its called pyrogis [4] for making custom image manipulations through numpy arrays.

https://github.com/PyO3/setuptools-rust