PyO3 provides some handy traits to convert between Python types and Rust types.

The easiest way to convert a python object to a rust value is using .extract()?.

ToPyObject trait is a conversion trait that allows various objects to be converted into PyObject. IntoPyObject serves the same purpose except it consumes self.

IntoPyTuple trait is a conversion trait that allows various objects to be converted into PyTuple object.

For example, IntoPyTuple trait is implemented for () so that you can convert it into a empty PyTuple

extern crate pyo3;
use pyo3::{Python, IntoPyTuple};

fn main() {
    let gil = Python::acquire_gil();
    let py = gil.python();
    let py_tuple = ().into_tuple(py);
}

There are several way how to pass positional and keyword arguments to python object call. ObjectProtocol trait provides two methods:

• call - call callable python object.
• call_method - call specific method on the object.

Both methods accept args and kwargs arguments. args argument is generate over IntoPyTuple trait. So args could be PyTuple instance or rust tuple with up to 10 elements. Or NoArgs object which represents empty tuple object.

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

# struct SomeObject;
# impl SomeObject {
#     fn new(py: Python) -> PyObject {
#           pyo3::PyDict::new(py).to_object(py)
#     }
# }
#
fn main() {
    # let arg1 = "arg1";
    # let arg2 = "arg2";
    # let arg3 = "arg3";

    let gil = Python::acquire_gil();
    let py = gil.python();

    let obj = SomeObject::new(py);

    // call object without empty arguments
    obj.call0(py);

    // call object with PyTuple
    let args = PyTuple::new(py, &[arg1, arg2, arg3]);
    obj.call1(py, args);

    // pass arguments as rust tuple
    let args = (arg1, arg2, arg3);
    obj.call1(py, args);
}

kwargs can by None or Some(&PyDict). You can use the IntoPyDict trait to convert other dict-like containers, e.g. HashMap, BTreeMap as well as tuples with up to 10 elements and Vecs where each element is a two element tuple.

extern crate pyo3;

use std::collections::HashMap;
use pyo3::prelude::*;

# struct SomeObject;
# impl SomeObject {
#     fn new(py: Python) -> PyObject {
#           pyo3::PyDict::new(py).to_object(py)
#     }
# }
fn main() {
    # let key1 = "key1";
    # let val1 = 1;
    # let key2 = "key2";
    # let val2 = 2;

    let gil = Python::acquire_gil();
    let py = gil.python();

    let obj = SomeObject::new(py);

    // call object with PyDict
    let kwargs = PyDict::new(py);
    kwargs.set_item(key1, val1);
    obj.call(py, NoArgs, kwargs);

    // pass arguments as rust tuple
    let kwargs = ((key1, val1), (key2, val2));
    obj.call(py, NoArgs, kwargs);

    // pass arguments as HashMap
    let mut kwargs = HashMap::<&str, i32>::new();
    kwargs.insert(key1, 1);
    obj.call(py, NoArgs, kwargs);
}

TODO