pyo3/README.md

# PyO3

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[Rust](http://www.rust-lang.org/) bindings for [Python](https://www.python.org/). This includes running and interacting with python code from a rust binaries as well as writing native python modules.

* User Guide: [stable](https://pyo3.rs) | [master](https://pyo3.rs/master)

* API Documentation: [master](https://pyo3.rs/master/doc)

A comparison with rust-cpython can be found [in the guide](https://pyo3.rs/master/rust-cpython.html).

## Usage

PyO3 supports Python 3.5 and up. The minimum required rust version is 1.34.0-nightly 2019-02-06.

PyPy is also supported (via cpyext) for Python 3.5 only, targeted PyPy version is 7.0.0.
Please refer to the guide for installation instruction against PyPy.

You can either write a native Python module in rust or use Python from a Rust binary.

However, on some OSs, you need some additional packages. E.g. if you are on *Ubuntu 18.04*, please run

```bash
sudo apt install python3-dev python-dev
```

## Using Rust from Python

PyO3 can be used to generate a native python module.

**`Cargo.toml`**

```toml
[package]
name = "string-sum"
version = "0.1.0"
edition = "2018"

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

[dependencies.pyo3]
version = "0.6.0"
features = ["extension-module"]
```

**`src/lib.rs`**

```rust
// Not required when using Rust 2018
extern crate pyo3;

use pyo3::prelude::*;
use pyo3::wrap_pyfunction;

#[pyfunction]
/// Formats the sum of two numbers as string
fn sum_as_string(a: usize, b: usize) -> PyResult<String> {
    Ok((a + b).to_string())
}

/// This module is a python module implemented in Rust.
#[pymodule]
fn string_sum(py: Python, m: &PyModule) -> PyResult<()> {
    m.add_wrapped(wrap_pyfunction!(sum_as_string))?;

    Ok(())
}
```

On Windows and Linux, you can build normally with `cargo build --release`. On MacOS, you need to set additional linker arguments. One option is to compile with `cargo rustc --release -- -C link-arg=-undefined -C link-arg=dynamic_lookup`, the other is to create a `.cargo/config` with the following content:

```toml
[target.x86_64-apple-darwin]
rustflags = [
  "-C", "link-arg=-undefined",
  "-C", "link-arg=dynamic_lookup",
]
```

For developing, you can copy and rename the shared library from the target folder: On MacOS, rename `libstring_sum.dylib` to `string_sum.so`, on Windows `libstring_sum.dll` to `string_sum.pyd` and on Linux `libstring_sum.so` to `string_sum.so`. Then open a Python shell in the same folder and you'll be able to `import string_sum`.

To build, test and publish your crate as Python module, you can use [pyo3-pack](https://github.com/PyO3/pyo3-pack) or [setuptools-rust](https://github.com/PyO3/setuptools-rust). You can find an example for setuptools-rust in [examples/word-count](examples/word-count), while pyo3-pack should work on your crate without any configuration.

## Using python from rust

Add `pyo3` this to your `Cargo.toml`:

```toml
[dependencies]
pyo3 = "0.6.0-alpha.4"
```

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

```rust
// Not required when using Rust 2018
extern crate pyo3;

use pyo3::prelude::*;
use pyo3::types::IntoPyDict;

fn main() -> PyResult<()> {
    let gil = Python::acquire_gil();
    let py = gil.python();
    let sys = py.import("sys")?;
    let version: String = sys.get("version")?.extract()?;
    let locals = [("os", py.import("os")?)].into_py_dict(py);
    let code = "os.getenv('USER') or os.getenv('USERNAME') or 'Unknown'";
    let user: String = py.eval(code, None, Some(&locals))?.extract()?;
    println!("Hello {}, I'm Python {}", user, version);
    Ok(())
}
```

## Examples and tooling

 * [examples/word-count](examples/word-count) _Counting the occurrences of a word in a text file_
 * [hyperjson](https://github.com/mre/hyperjson) _A hyper-fast Python module for reading/writing JSON data using Rust's serde-json_
 * [rust-numpy](https://github.com/rust-numpy/rust-numpy) _Rust binding of NumPy C-API_
 * [html-py-ever](https://github.com/PyO3/setuptools-rust/tree/master/html-py-ever) _Using [html5ever](https://github.com/servo/html5ever) through [kuchiki](https://github.com/kuchiki-rs/kuchiki) to speed up html parsing and css-selecting._
 * [pyo3-built](https://github.com/PyO3/pyo3-built) _Simple macro to expose metadata obtained with the [`built`](https://crates.io/crates/built) crate as a [`PyDict`](https://pyo3.github.io/pyo3/pyo3/struct.PyDict.html)_
 * [point-process](https://github.com/ManifoldFR/point-process-rust/tree/master/pylib) _High level API for pointprocesses as a Python library_
 * [autopy](https://github.com/autopilot-rs/autopy) _A simple, cross-platform GUI automation library for Python and Rust._
 * [orjson](https://github.com/ijl/orjson)  _Fast Python JSON library_

## License

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).