Re: instantiating python objects within C++

Hi Adam,

Adam Hupp wrote:

> Try looking at libs/python/test/embedding.cpp.  It has a nice example
> of this usage.  

thanks for the pointer. I looked, but the main question is still
unanswered, as the example instantiates an object 'implemented' in
python (derived from a C++ type). Do I really have to run the
interpreter to instantiate a python-wrapper-object around my own type ?

Anyways, I tried and failed. I attach the test, may be someone can
see what I'm doing wrong...

Running the compiled program (which calls 'script.py') results in
the following output:

<code object ? at 0x8120068, file "null", line 1>
<type 'code'>
python exception
Traceback (most recent call last):
  File "script.py", line 3, in ?
    object.value = 42
TypeError: 'code' object has only read-only attributes (assign to .value)


Thanks a lot,
                Stefan
#include <boost/python.hpp>
#include <boost/python/extract.hpp>
#include <boost/python/dict.hpp>
#include <boost/python/class.hpp>

#include <iostream>
#include <fstream>
#include <sstream>
#include <memory>
#include <string>

class Foo
{
public:
   Foo() : mValue(0) {}
   void SetValue(int i) { mValue = i;}
   int GetValue() const { return mValue;}
private:
   int mValue;
};

namespace python = boost::python;

BOOST_PYTHON_MODULE(Sandbox)
{
   python::class_<Foo> foo("Foo");
   foo.add_property("value", &Foo::GetValue, &Foo::SetValue);
}

int main(int, char **)
{
   PyImport_AppendInittab("Sandbox", initSandbox);
   Py_Initialize();
   python::handle<> 
main_module(python::borrowed(PyImport_AddModule("__main__")));
   python::dict main_namespace = 
python::dict(python::handle<>(python::borrowed(PyModule_GetDict(main_module.get()))));

   try
   {
      python::handle<> FooType(Py_CompileString("from Sandbox import *  \n"
                                                "Foo                    \n",
                                                "null",
                                                Py_file_input));
      
      python::object foo(FooType);

      main_namespace["object"] = foo;
      FILE *fp = fopen("script.py", "r");
      python::handle<> result(PyRun_File(fp, "script.py", Py_file_input,
                                         main_namespace.ptr(), 
main_namespace.ptr()));
      Foo &foo1 = python::extract<Foo &>(main_namespace["object"]);
      std::cout << foo1.GetValue() << std::endl;
   }
   catch(const python::error_already_set &)
   {
      std::cout << "python exception" << std::endl;
      PyErr_Print();
   }
   Py_Finalize();
}
print object
print type(object)
object.value = 42