Python Code

Assume we have the following Python code that we would like to call from Rust:

def join(s1, s2):
    # Joins the strings s1 and s2
    return s1 + ' ' + s2

Python Setup

We need to ensure the module is visible to the Python interpreter. One way this can be done is by modifying the PYTHONPATH environment variable to include the path to the module:

export PYTHONPATH="${PYTHONPATH}:/path/to/your/module/"

Rust Setup

We can utilize the pyo3 crate to take care of the Rust bindings to the Python interpreter:

[dependencies]
pyo3 = "0.11"

Call Python code from Rust

Now we can use pyo3 to import and call our Python module from Rust:

use pyo3::{prelude::*, types::{PyTuple, PyString}};

fn call_python_function() -> PyResult<String> {
    // Acquire the Python Globabl Interpreter Lock
    let gil = Python::acquire_gil();
    let py = gil.python();

    // Import my Python module
    let module = py.import("my_module")?;

    // Create an array of Python Strings
    let args = [
        PyString::new(py, "Hello"),
        PyString::new(py, "World"),
    ];

    // Call the Python function "join" with some arguments
    let result = module.call1(
        "join", 
        PyTuple::new(py, args),
    )?;

    let result: String = result.extract()?;

    Ok(result)
}

fn main() {
    match call_python_function() {
        Ok(result) => println!("Python function returned: {}", result),
        Err(err) => eprintln!("Error calling Python function: {:?}", err.ptraceback),
    }
}

Upon running we see the output: Python function returned: Hello World