[C++-sig] call Python function from C++ without copying the arguments

[Sebastian Walter]

Hello,

I want to call a Python function from C++ with an object of a C++ class
as argument.
The Python-function should change the argument, so changes are visible
on the C++ side.
Boost::Python automatically makes a copy of all the arguments that are
passed to a callable Python object.

Is there a way NOT to copy all arguments??

Below sample code:
The desired output of $python test.py would be

- ----------- desired output ---------------
a.x=0
a.x=12345


- ----------- test.cpp ---------------

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

using namespace std;
using namespace boost;
using namespace boost::python;

class A{
        public:
        int x;
        A(){x=0;}
};

void my_test_function(object fun_obj){
        A a;
        cout<<"a.x="<<a.x<<endl;
        fun_obj(a);
        cout<<"a.x="<<a.x<<endl;
}

BOOST_PYTHON_MODULE(_test)
{
        def("my_test_function", my_test_function);
        class_<A>("A", init<>())
        .def_readwrite("x", &A::x);
}


- ----------- test.py ---------------
from _test import *

def f(a):
        a.x = 12345


Thanks in advance,
Sebastian Walter



-- 
Sebastian Walter

Institut fuer Mathematik, Humboldt-Universitaet    Tel: +49 (30) 2093-5869
Rudower Chaussee 25, Adlershof, Berlin             Fax: +49 (30) 2093-5859
Post: Unter den Linden 6, D-10099 Berlin         Email: 
walter at mathematik.hu-berlin.de
WWW: http://www.mathematik.hu-berlin.de/~walter