Re: python: returning objects as PyObject* from memberfunction

From: rwgk_at_[hidden]
Date: 2001-08-24 02:34:44

You could try something like this:

PyObject* MyObjectB::mem_function(params) {
        MyObjectA retVal;
        if (ok)
                return BOOST_PYTHON_CONVERSION::to_python(retVal);
        else
                return boost::python::detail::none();
}

The instationation of class_builder<MyObjectA> must appear
*before* you use the to_python converter.

Related examples: do_it_yourself_cvts.cpp, pickle3.cpp.
do_it_yourself_cvts.cpp shows how you can fill a Python
list with your objects.

Another detail: I believe it would be best if your member
function returns a boost::python::ref. Only to_python
converters should return a bar PyObject*.
If you have a reason to stick with PyObject* as the
return value anyway, test your code for memory leaks.
Under Unix this is very easy: call the method a millon
times and monitor the memory allocation with the
"top" command.

Ralf

--- In boost_at_y..., "Achim Domma" <achim.domma_at_s...> wrote:
> Hi,
> 
> is there a possibility to convert instances of objects, which are 
registert
> in my module, to PyObjects*. The following works fine :
> 
> MyObjectA MyObjectB::mem_function(params) {
> 	MyObjectA retVal;
> 	...
> 	return retVal;
> }
> 
> but this way I can't return 'None'. So I tried the following:
> 
> PyObject* MyObjectB::mem_function(params) {
> 	MyObjectA retVal;
> 	if (ok)
> 		return retVal; // <- how to convert ???
> 	else
> 		return boost::details::none();
> }
> 
> How can I get a PyObject out of my C++ Instance ? The same problem 
arrises
> if I try to fill a python list with my own objects.
> 
> I tried to find a solution in the sources and via groups.google.com 
but
> could not find anything. If there is a solution I would be 
absolutly happy
> with as point I can start searching.
> 
> greetings
> Achim