pybind11 でキーワード引数 (kwargs) を使う

#include <pybind11/embed.h>
#include <pybind11/pybind11.h>

namespace py = pybind11;

int main()
{
    // python インタプリタを起動する
    py::scoped_interpreter interpreter;

    // numpy の各種オブジェクトを取得する
    py::module numpy = pybind11::module::import("numpy");
    py::object zeros = numpy.attr("zeros");
    py::object float32 = numpy.attr("float32");
    py::object int32 = numpy.attr("int32");

    // numpy.ndarray を作る
    py::object f32_array = zeros(10, py::arg("dtype") = float32);
    py::object i32_array = zeros(10, py::arg("dtype") = int32);

    // 配列の文字列表現を標準出力に書き出す
    py::print(py::repr(f32_array));
    py::print(py::repr(i32_array));

    return 0;
}

$ # M1 Mac (Monterey) + Python 3.8.9 + pybind11 2.9.2 (Homebrew)
$ clang sample.cpp -std=c++20 -lc++ -lpython3.8 -rpath /Library/Developer/CommandLineTools/Library/Frameworks -I/Library/Developer/CommandLineTools/Library/Frameworks/Python3.framework/Versions/3.8/Headers -I/opt/homebrew/Cellar/pybind11/2.9.2/include -L/Library/Developer/CommandLineTools/Library/Frameworks/Python3.framework/Versions/3.8/lib -o sample

$ ./sample
array([0., 0., 0., 0., 0., 0., 0., 0., 0., 0.], dtype=float32)
array([0, 0, 0, 0, 0, 0, 0, 0, 0, 0], dtype=int32)

#include <pybind11/embed.h>
#include <pybind11/pybind11.h>
#include <utility>

namespace py = pybind11;
using std::pair;

void hello(py::args args, py::kwargs kwargs)
{
    for (const py::handle& arg : args)
    {
        py::print(py::str(arg));
    }
    for (const pair<py::handle, py::handle>& kv : kwargs)
    {
        py::print(py::str(kv.first), "=", py::str(kv.second));
    }
}

int main()
{
    // python インタプリタを起動する
    py::scoped_interpreter interpreter;

    // main モジュール上に hello 関数を定義する
    py::module main_module = py::module::import("__main__");
    main_module.def("hello", &hello);

    // python スクリプトから hello 関数を呼び出す
    py::object scope = main_module.attr("__dict__");
    py::exec("hello('hello', a = 1, b = 2, abc = 123)", scope);

    return 0;
}

$ # M1 Mac (Monterey) + Python 3.8.9 + pybind11 2.9.2 (Homebrew)
$ clang sample2.cpp -std=c++20 -lc++ -lpython3.8 -rpath /Library/Developer/CommandLineTools/Library/Frameworks -I/Library/Developer/CommandLineTools/Library/Frameworks/Python3.framework/Versions/3.8/Headers -I/opt/homebrew/Cellar/pybind11/2.9.2/include -L/Library/Developer/CommandLineTools/Library/Frameworks/Python3.framework/Versions/3.8/lib -o sample2

$ ./sample2
hello
a = 1
b = 2
abc = 123