buildcommand.sh

c++ -O3 -Wall -shared -std=c++11 -fPIC `python -m pybind11 --includes` example.cpp -o _example`python-config --extension-suffix`

example.cpp

#include <string>
#include <sstream>
#include <pybind11/pybind11.h>
#include <pybind11/functional.h>


namespace py = pybind11;


typedef void (*cbfunc) (void*, const void*);


class Example {
private:
    cbfunc m_cb;

public:
    Example();
    int m_add(int i, int j);
    void m_setCallback(cbfunc cb);
};


Example::Example() {
    m_cb = NULL;
}


int Example::m_add(int i, int j) {
    if (m_cb) {
        std::ostringstream oss;

        oss << "Adding " << i << " and " << j;
        m_cb(NULL, static_cast<const void*>(oss.str().c_str()));
    }

    return i + j;
}


void Example::m_setCallback(cbfunc cb) {
    m_cb = cb;
}


static std::function<void(char *, const char *)> example_cb;


PYBIND11_MODULE(_example, m) {
        m.doc() = "This is an example plugin\n"
                  "\n"
                  "Yey!";
    py::class_<Example>(m, "Example")
        .def(py::init<>())
        .def("add", &Example::m_add)
        .def("set_callback", [](Example &self, std::function<void(char*, const char*)> cb) {
            example_cb = cb;
            self.m_setCallback(+[](void* a, const void* b) {
                example_cb(static_cast<char*>(a), static_cast<const char*>(b));
            });
        });
}

example.py

import _example


def cb(*args):
    print(args)


class A:
    def __init__(self):
        self.ex = _example.Example()
        self.ex.set_callback(cb)

    def foo(self):
        print(self.ex.add(1, 2))


a = A()
a.foo()