Rust is super fast. Python is super flexible. Porting slow python code to rust can make your life a lot easier, and it’s not too difficult to set up.

I will demonstrate rust bindings for summing the integers in a large text file containing a billion digits that looks like

6,9,8,3,0,1,8,4,9,7,6,3,4,2,6,0,0,5,1,1, . . . ,4,5,9,3,3,2,8,3

General steps

  1. install rust and maturin
  2. set up boilerplate
  3. add your function
  4. compile and import

Install Rust and Maturin

curl --proto '=https' --tlsv1.2 -sSf | sh
pip install maturin

See also install rust and install maturin

Set up boilerplate

# select "pyo3" here
maturin new cool_rust_bindings
cd cool_rust_bindings

Add your function

Open src/ and change it to the following:

use pyo3::prelude::*;
use std::fs::File;
use std::io::{self, Read};

fn sum_file(filename:&str) -> io::Result<i64> {
    let mut file = File::open(filename)?;
    let mut contents = String::new();
    file.read_to_string(&mut contents)?;

    let mut total:i64 = 0;
    for x in contents.chars() {
        if x != ','{
            total += (x as i64) - 48;


fn cool_rust_bindings(_py: Python, m: &PyModule) -> PyResult<()> {
    m.add_function(wrap_pyfunction!(sum_file, m)?)?;

Here we’re just creating a simple function that sums the integers in a file. The rust code gave a 3x speedup over the corresponding python code. Depending on the task, I’ve gotten 10-20x speedups.

Compile and import

Run the following from the cool_rust_bindings directory

maturin develop

This will add cool_rust_bindings to your python path. Use it like

import cool_rust_bindings