# PyO3
[](https://travis-ci.org/PyO3/pyo3) [](https://ci.appveyor.com/project/fafhrd91/pyo3) [](https://codecov.io/gh/PyO3/pyo3) [](https://crates.io/crates/pyo3) [](https://gitter.im/PyO3/Lobby)
[Rust](http://www.rust-lang.org/) bindings for the [Python](https://www.python.org/) interpreter. 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](https://docs.rs/crate/pyo3/)
A comparison with rust-cpython can be found [in the guide](https://pyo3.rs/master/rust-cpython.html).
## Usage
Pyo3 supports python 2.7 as well as python 3.5 and up. The minimum required rust version is 1.27.0-nightly 2018-05-01.
### From a rust binary
To use `pyo3`, add this to your `Cargo.toml`:
```toml
[dependencies]
pyo3 = "0.3"
```
Example program displaying the value of `sys.version`:
```rust
#![feature(use_extern_macros, specialization)]
extern crate pyo3;
use pyo3::prelude::*;
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 = 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(())
}
```
### As native module
Pyo3 can be used to generate a python-compatible library.
**`Cargo.toml`:**
```toml
[package]
name = "rust2py"
version = "0.1.0"
[lib]
name = "rust2py"
crate-type = ["cdylib"]
[dependencies.pyo3]
version = "0.3"
features = ["extension-module"]
```
**`src/lib.rs`**
```rust
#![feature(use_extern_macros, specialization)]
extern crate pyo3;
use pyo3::prelude::*;
// 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]
fn rust2py(py: Python, m: &PyModule) -> PyResult<()> {
#[pyfn(m, "sum_as_string")]
// ``#[pyfn()]` 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(())
}
// The logic can be implemented as a normal rust function
fn sum_as_string(a:i64, b:i64) -> String {
format!("{}", a + b).to_string()
}
```
On windows and linux, you can build normally with `cargo build --release`. On Mac Os, 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",
]
```
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.
[`setuptools-rust`](https://github.com/PyO3/setuptools-rust) can be used to generate a python package and includes the commands above by default. See [examples/word-count](examples/word-count) and the associated setup.py.
## 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).