Boost-python 如何将C++类实例传递给Python类

Question

我刚接触boost python。我的任务是先在C++代码中初始化一个类的实例，然后把这个C++实例传给Python代码，接着用Python类的实例来调用它（也就是这个C++实例）。我试过用Python/C API的方法，但没有成功，所以我想知道怎么把一个C++类的实例传给Python类。

以下是我的代码，是从boost python的示例中改过来的。

在main.cpp中

#include <python2.6/Python.h>
#include <boost/python.hpp>
#include <iostream>

using namespace boost::python;
using namespace std;

class World
{
private:
    string name;
public:
    void set(string name)
    {
        this->name = name;
    }
    void greet()
    {
        cout << "hello, I am " << name << endl;
    }
};

typedef boost::shared_ptr< World > world_ptr;

BOOST_PYTHON_MODULE(hello)
{
    class_<World>("World")
    .def("greet", &World::greet)
    .def("set", &World::set)
    ;

    register_ptr_to_python<world_ptr>();
};

int main()
{
    Py_Initialize();
    PyRun_SimpleString("import sys");
    PyRun_SimpleString("sys.path.append('./')");

    world_ptr worldObjectPtr (new World);
    worldObjectPtr->set("C++!");

    try
    {
        inithello();
        PyObject* pModule =PyImport_ImportModule("python");
        PyObject* pDict = PyModule_GetDict(pModule);
        PyObject* pClassHelloPython = PyDict_GetItemString(pDict, "Person");
        PyObject* pInstanceHelloPython = PyInstance_New(pClassHelloPython, NULL, NULL);

        PyObject_CallMethod(pInstanceHelloPython, "sayHi", NULL);
        worldObjectPtr->greet();
        PyObject_CallMethod(pInstanceHelloPython, "greetReset", "O", worldObjectPtr);
        worldObjectPtr->greet();
    }
    catch (error_already_set)
    {
        PyErr_Print();
    }

    Py_Finalize();

    return 0;
}

在python.py中

class Person:
    def sayHi(self):
        print 'hello from python'

    def greetReset(self, instance):
        instance.set('Python')

在上面的代码中，我想把worldObjectPtr传给pInstanceHelloPython，这样pInstanceHelloPython就可以把worldObjectPtr->name设置为Python。但是我就是不知道该怎么做。谢谢你们的耐心帮助！！

Answer 1

通过使用boost::python::ptr将对象指针传递给Python。这样可以防止Python解释器创建对象的副本：

#include <boost/python.hpp>
#include <string>
#include <iostream>

using namespace boost::python;
using namespace std;

class World
{
private:
    string name;
public:
    void set(string name) {
        this->name = name;
    }
    void greet() {
        cout << "hello, I am " << name << endl;
    }
};

typedef boost::shared_ptr< World > world_ptr;

BOOST_PYTHON_MODULE(hello)
{
    class_<World>("World")
        .def("greet", &World::greet)
        .def("set", &World::set)
    ;
};

int main(int argc, char **argv)
{
    Py_Initialize();
    try {
        PyRun_SimpleString(
            "class Person:\n"
            "    def sayHi(self):\n"
            "        print 'hello from python'\n"
            "    def greetReset(self, instance):\n"
            "        instance.set('Python')\n"
          );

        world_ptr worldObjectPtr (new World);
        worldObjectPtr->set("C++!");

        inithello();
        object o_main 
            = object(handle<>(borrowed(PyImport_AddModule("__main__"))));
        object o_person_type = o_main.attr("Person");
        object o_person = o_person_type();
        object o_func1 = o_person.attr("sayHi");
        o_func1();
        object o_func2 = o_person.attr("greetReset");
        o_func2(boost::python::ptr(worldObjectPtr.get()));
        worldObjectPtr->greet();
    }
    catch (error_already_set) {
        PyErr_Print();
    }

    Py_Finalize();

    return 0;
}