Unpacking C++ type in Python with Pybind11

demo.cpp

#include <pybind11/pybind11.h>

namespace py = pybind11;

struct Size {
    double width, height;
};

PYBIND11_MODULE(demo, m) {
    py::class_<Size>(m, "Size")
        .def(py::init<double, double>())
        .def_readwrite("width", &Size::width)
        .def_readwrite("height", &Size::height)
        .def("__iter__", [](Size const& v) {
            return py::iter(py::make_tuple(v.width, v.height));
        });
}