Some examples of rust to python using cpython (for my own reference)

Cargo.toml

[package]
name = "my_module"
version = "0.1.0"
authors = ["Jason Dixon <--->"]
edition = "2018"

[lib]
name = "my_module"
crate-type = ["cdylib"]

[dependencies.cpython]
version = "0.2"
features = ["extension-module"]

[dependencies]

lib.rs

#[macro_use] extern crate cpython;

use cpython::{PyResult, Python, PyErr, PyObject};
use cpython::exc::RuntimeError;
use std::thread::sleep;
use std::time::Duration;

py_class!(class MyClass |py| {
    data some_data: String;

    def __new__(_cls, data: String) -> PyResult<MyClass> {
        MyClass::create_instance(py, data)
    }

    @classmethod def from_int(_cls, data: i32) -> PyResult<MyClass> {
        MyClass::create_instance(py, data.to_string())
    }

    def get_data(&self) -> PyResult<String> {
        let data = self.some_data(py).clone();
        Ok(data)
    }

    def __repr__(&self) -> PyResult<String> {
        Ok(format!("MyClass <{}>", self.some_data(py)))
    }

    def sleep(&self) -> PyResult<PyObject> {
        // Drop the GIL to do some work.
        py.allow_threads(|| {
            println!("About to nap...");
            sleep(Duration::from_secs(4));
            println!("Waking up!");
        });
        Ok(py.None())
    }

    def error(&self, doit: bool) -> PyResult<PyObject> {
        if doit {
            Err(PyErr::new::<RuntimeError, _>(py,  "Oops, what an error."))
        } else {
            Ok(py.None())
        }
    }

    def version(&self) -> PyResult<String> {
        let sys = py.import("sys")?;
        Ok(sys.get(py, "version")?.extract(py)?)
    }
});

fn my_function(_: Python, name: &str) -> PyResult<String> {
    Ok(format!("Hello {}", name))
}

// May need "libmy_module"
py_module_initializer!(libmy_module, initlibmy_module, PyInit_my_module, |py, m| {
    m.add(py, "__doc__", "This module is implemented in Rust.")?;
    m.add(py, "my_function", py_fn!(py, my_function(name: &str)))?;
    m.add_class::<MyClass>(py)?;
    Ok(())
});