The following message is a courtesy copy of an article that has been posted to comp.lang.python as well. Dear Mr. Handheld Vacuum, You will probably get better answers to your Boost.Python questions if you post them to the C++-sig. See http://www.boost.org/more/mailing_lists.htm#Cplussig. thedustbustr@aol.com (TheDustbustr) writes:

I'm writing a game in C++ which calls out to python for scripting. I'd like to expose the instance of my Game class (a singleton) to python (so that the instances of Clock, Camera, etc are available to the scripts).

I ran into trouble trying to expose a specific instance (or even a function returning the instance). Here is a simplification of my problem in code (c++):

<code> class A{ public: int i; }; class B{ public: A a; }; B b; B getb() {return b;} //return the instance

int main() { getb().a.i = 42; return 0;} #include <boost/python/module.hpp> #include <boost/python/class.hpp> #include <boost/python/def.hpp> using namespace boost::python; BOOST_PYTHON_MODULE(hello) { class_<A>("A",init<>()) .def("i", &A::i); class_<B>("B",init<>()) .def("a", &B::a); def("getb", getb); } </code>

Of course, I would be calling any python script using these classes from within main().

This doesn't compile (using bjam with msvc). If I return by reference or pointers in getb it gets ugly (like pages and pages of error messages). Am I doing this the right way? How do I expose an instance to python?

-- Dave Abrahams Boost Consulting www.boost-consulting.com