pyo3/README.md

# PyO3 [![Build Status](https://travis-ci.org/PyO3/pyo3.svg?branch=master)](https://travis-ci.org/PyO3/pyo3) [![Build Status](https://ci.appveyor.com/api/projects/status/github/PyO3/pyo3?branch=master&svg=true)](https://ci.appveyor.com/project/fafhrd91/pyo3) [![codecov](https://codecov.io/gh/PyO3/pyo3/branch/master/graph/badge.svg)](https://codecov.io/gh/PyO3/pyo3) [![crates.io](http://meritbadge.herokuapp.com/pyo3)](https://crates.io/crates/pyo3) [![Join the dev chat](https://img.shields.io/gitter/room/nwjs/nw.js.svg)](https://gitter.im/PyO3/Lobby)

[Rust](http://www.rust-lang.org/) bindings for the [Python](https://www.python.org/) interpreter.

* [User Guide](https://pyo3.github.io/pyo3/guide/)
* [API Documentation](http://pyo3.github.io/pyo3/pyo3/)
* Cargo package: [pyo3](https://crates.io/crates/pyo3)

---

PyO3 is licensed under the [Apache-2.0 license](http://opensource.org/licenses/APACHE-2.0).
Python is licensed under the [Python License](https://docs.python.org/2/license.html).

Supported Python versions:

* Python 2.7, Python 3.5 and up

Supported Rust version:

* Rust 1.23.0-nightly 2017-11-07 or later

## Usage

To use `pyo3`, add this to your `Cargo.toml`:

```toml
[dependencies]
pyo3 = "0.2"
```

Example program displaying the value of `sys.version`:

```rust
extern crate pyo3;

use pyo3::{Python, PyDict, PyResult, ObjectProtocol};

fn main() {
    let gil = Python::acquire_gil();
    hello(gil.python()).unwrap();
}

fn hello(py: Python) -> PyResult<()> {
    let sys = py.import("sys")?;
    let version: String = sys.get("version")?.extract()?;

    let locals = PyDict::new(py);
    locals.set_item("os", py.import("os")?)?;
    let user: String = py.eval("os.getenv('USER') or os.getenv('USERNAME')", None, Some(&locals))?.extract()?;

    println!("Hello {}, I'm Python {}", user, version);
    Ok(())
}
```

Example library with python bindings:

The following two files will build with `cargo build`, and will generate a python-compatible library.
For MacOS, "-C link-arg=-undefined -C link-arg=dynamic_lookup" is required to build the library.
`setuptools-rust` includes this by default.
See [examples/word-count](examples/word-count) and the associated setup.py.
Also on macOS, you will need to rename the output from \*.dylib to \*.so.
On Windows, you will need to rename the output from \*.dll to \*.pyd.


**`Cargo.toml`:**

```toml
[lib]
name = "rust2py"
crate-type = ["cdylib"]

[dependencies.pyo3]
version = "0.2"
features = ["extension-module"]
```

**`src/lib.rs`**

```rust
#![feature(proc_macro, specialization)]

extern crate pyo3;
use pyo3::prelude::*;

use pyo3::py::modinit as pymodinit;

// add bindings to the generated python module
// N.B: names: "librust2py" must be the name of the `.so` or `.pyd` file
/// This module is implemented in Rust.
#[pymodinit(rust2py)]
fn init_mod(py: Python, m: &PyModule) -> PyResult<()> {

    #[pyfn(m, "sum_as_string")]
    // pyo3 aware function. All of our python interface could be declared in a separate module.
    // Note that the `#[pyfn()]` annotation automatically converts the arguments from
    // Python objects to Rust values; and the Rust return value back into a Python object.
    fn sum_as_string_py(a:i64, b:i64) -> PyResult<String> {
       let out = sum_as_string(a, b);
       Ok(out)
    }

    Ok(())
}

// logic implemented as a normal rust function
fn sum_as_string(a:i64, b:i64) -> String {
    format!("{}", a + b).to_string()
}

```

For `setup.py` integration, see [setuptools-rust](https://github.com/PyO3/setuptools-rust)


**This is fork of rust-cpython project https://github.com/dgrunwald/rust-cpython**

[Motivation for fork](https://github.com/PyO3/pyo3/issues/55)