[C++-sig] Re: Creating an instance of a Python class in C++: PyRun_String?

Dirk Gerrits dirk at gerrits.homeip.net
Fri Nov 15 08:53:58 CET 2002

David Abrahams wrote:

> Dirk Gerrits  writes:
> >Dirk Gerrits wrote:
> >
> >
> >>Firstly, I don't know which arguments to feed into PyRun_String. The
> >>python.org docs didn't really help me that much: I don't have any
> >>dictionaries of globals and locals, and what exactly is a start
> >>token?
> >
> >Upon further RTFMing on start tokens, I tried this:
> >
> >// Create and use an instance of the Python derived class
> >Base* py = python::extract(
> >     PyRun_String("PythonDerived()\n", Py_eval_input, 0, 0));
> >py->f();
> >
> >This gives an access violation in find_instance_impl which is called
> >by extract_pointer::extract_pointer(PyObject* obj) as far as I
> >can tell. And the Base& version wouldn't compile as I said.
> >
> >What (else) am I doing wrong?
> Does
>    http://www.boost.org/libs/python/doc/v2/extract.html#examples
> help?

I looked at that one, as I said in my initial post. However the example 
creates a new python::object instance of a wrapped C++ class. Not of a 
Python class. Is there some way to create a class_ object from a Python 
class that I'm not aware of?

I don't really see how the example would compile BTW, because value is 
declared a non-const member function and it is called through the const 
reference x.


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