Extend pyproject.toml example to include a Rust entry-point

examples/hello-world-pyprojecttoml/noxfile.py

@@ -14,6 +14,7 @@ def test(session: nox.Session):
     session.run("print-hello")
     # Test script wrapper for Python entry-point
     session.run("sum-cli", "5", "7")
+    session.run("rust-demo", "5", "7")
     # Test library
     session.run("pytest", "tests", *session.posargs)
     session.run("python", "-c", "from hello_world import _lib; print(_lib)")

examples/hello-world-pyprojecttoml/pyproject.toml

@@ -1,22 +1,31 @@
 [build-system]
-requires = ["setuptools", "wheel", "setuptools-rust"]
+requires = ["setuptools", "setuptools-rust"]
 build-backend = "setuptools.build_meta"
 
 [project]
 name = "hello-world"
 version = "1.0"
 
-[project.scripts]  # Python entry-point wrapper to be installed in `$venv/bin`
-sum-cli = "hello_world.sum_cli:main"
+[project.scripts]
+# Python entry-point wrapper to be installed in `$venv/bin`
+sum-cli = "hello_world.sum_cli:main"  # Python function that uses Rust
+rust-demo = "hello_world._lib:demo"   # Rust function that uses Python
 
-[tool.setuptools.packages]  # pure Python packages/modules
+[tool.setuptools.packages]
+# Pure Python packages/modules
 find = { where = ["python"] }
 
 [[tool.setuptools-rust.ext-modules]]
-target = "hello_world._lib"  # private module to be nested into Python package
-py-limited-api = "auto"
-args = ["--profile", "release-lto"]
+# Private Rust extension module to be nested into Python package
+target = "hello_world._lib"  # The last part of the name (e.g. "_lib") has to match lib.name in Cargo.toml,
+                             # but you can add a prefix to nest it inside of a Python package.
+py-limited-api = "auto"  # Default value, can be omitted
+binding = "PyO3"  # Default value, can be omitted
+# See reference for RustExtension in https://setuptools-rust.readthedocs.io/en/latest/reference.html
 
-[[tool.setuptools-rust.binaries]]  # executable to be installed in `$venv/bin`
-target = "print-hello"
-args = ["--profile", "release-lto"]
+[[tool.setuptools-rust.binaries]]
+# Rust executable to be installed in `$venv/bin`
+target = "print-hello"  # Needs to match bin.name in Cargo.toml
+args = ["--profile", "release-lto"]  # Extra args for Cargo
+# See reference for RustBin in https://setuptools-rust.readthedocs.io/en/latest/reference.html
+# Note that you can also use Python entry-points as alternative to Rust binaries

examples/hello-world-pyprojecttoml/python/hello_world/sum_cli.py

@@ -1,7 +1,7 @@
 import argparse
 import sys
 
-from . import sum_as_string
+from ._lib import sum_as_string
 
 
 def main():

examples/hello-world-pyprojecttoml/rust/lib.rs

@@ -1,16 +1,35 @@
 use pyo3::prelude::*;
+use std::env;
 
 /// Formats the sum of two numbers as string.
 #[pyfunction]
 fn sum_as_string(a: usize, b: usize) -> PyResult<String> {
     Ok((a + b).to_string())
 }
 
+/// Calls Python (see https://pyo3.rs for details)
+#[pyfunction]
+fn demo(py: Python) -> PyResult<()> {
+    let argv = env::args().collect::<Vec<_>>();
+    println!("argv = {:?}", argv);
+    // argv[0]: Python path, argv[1]: program name, argv[2..]: given args
+
+    let numbers: Vec<i32> = argv[2..].iter().map(|s| s.parse().unwrap()).collect();
+
+    Python::with_gil(|py| {
+        let python_sum = PyModule::import(py, "builtins")?.getattr("sum")?;
+        let total: i32 = python_sum.call1((numbers,))?.extract()?;
+        println!("sum({}) = {:?}", argv[2..].join(", "), total);
+        Ok(())
+    })
+}
+
 /// A Python module implemented in Rust. The name of this function must match
 /// the `lib.name` setting in the `Cargo.toml`, else Python will not be able to
 /// import the module.
 #[pymodule]
 fn _lib(_py: Python<'_>, m: &PyModule) -> PyResult<()> {
     m.add_function(wrap_pyfunction!(sum_as_string, m)?)?;
+    m.add_function(wrap_pyfunction!(demo, m)?)?;
     Ok(())
 }