The aim here is to write a library in Rust and call it from Python using ctypes.

Example 1: Hello World

Cargo.toml

[package]
name = "capi1"
version = "0.1.0"
edition = "2021"

[lib]
name = "capi1"
crate-type = ["rlib", "cdylib"]

[dependencies]

lib.rs

use std::ffi::{CStr,CString};
use std::os::raw::c_char;

#[no_mangle]
pub extern "C" fn hello_world() {
    println!("Hello world");
}

#[no_mangle]
pub extern "C" fn hello(s: *const c_char ) {
    if s.is_null() {
        eprintln!("Received null pointer");
        return
    }

    unsafe {
        match CStr::from_ptr(s).to_str() {
            Ok(rust_str) => {
                println!("Hello {rust_str}!!");
            }
            Err(e) => {
                eprintln!("Failed to convert C string to Rust string: {}",e);
            }
        }
    }
}

hello.py

import ctypes

dll = ctypes.CDLL("./libcapi1.so")
hello_world = dll.hello_world
hello_world()

hello = dll.hello
hello("world".encode())