> How do I expose my C++ type to a user
> defined python type? I think I could use boost python
> class_<> wrapper to wrap around, but if I want to use
> to_python/from_python convertors?
>
> Say I want to expose my C++ class(CA) to a python
> type(PA):
>
> C++:
> class CA
> {
> public:
> //ctors, accessors...
> private:
> std::string name_;
> int value_;
> };
>
> Python:
> class PA(object):
> def __init__(self, name, value):
> self.name=name
> self.value=value
>
> If I use,
>
> void initializeConverters()
> {
> using namespace boost::python;
> to_python_converter<CA,
> CA_to_pA>();
> }
>
> with
>
> struct CA_to_PA
> {
> static PyObject* convert(CA const&
> s)
> {
> printf("In C++ ->
> python converter?\n");
>
> std::string
> name=s.name();
> int
> value=s.value();
>
> #if 0
> static
> boost::python::object obj;
> PyObject*
> obj_ptr=obj.ptr();
>
>
> PyObject_SetAttrString(obj_ptr, "name",
>
> PyString_FromString(name.c_str()));
>
> PyObject_SetAttrString(obj_ptr, "value",
>
> PyInt_FromLong(value));
>
> return
> boost::python::incref(obj_ptr);
> #else
> return
> boost::python::incref(
>
> //PyInt_FromLong(1999)
>
> Py_BuildValue("s", "native string works")
>
> //Py_BuildValue("{s:i,s:i}", "abc", 123, "def", 456)
> );
> #endif
> }
> };
>
> How do I create a boost::python::object (or PyObject*) with
> "name" and "value" attributes? I could get creation and
> return of python native types to work, but can not get user
> defined types returned to the python side -- always get
> NoneType returned.
>
> boost::python::object C2Py()
> {
> printf("Pre assignment\n");
>
> #if 0
> boost::python::object obj(new CA("From
> C++ to python", 987654321));
> PyObject* o=obj.ptr();
> #else
> CA a("From C++ to python", 987654321);
> PyObject *o=CA_to_PA::convert(a);
> #endif
>
> printf("Post assignment\n");
>
> PyObject *tmp=NULL;
>
> std::string name="No Name";
> int value=-1;
>
> tmp=PyObject_GetAttrString(o, "name");
> if (tmp!=NULL)
> name=PyString_AsString(tmp);
>
> tmp=PyObject_GetAttrString(o, "value");
> if (tmp!=NULL) value=PyInt_AsLong(tmp);
>
> printf("(%s, %d)\n", name.c_str(),
> value);
>
> return obj;
> }
>
> $ python
> Python 2.5.1 (r251:54863, Oct 5 2007, 11:16:46)
> [GCC 4.1.1 20070105 (Red Hat 4.1.1-53)] on linux2
> Type "help", "copyright", "credits" or "license" for more
> information.
> >>> import mytypes
> >>> pa=mytypes.C2Py()
> ("No Name", -1)
> >>>type(pa)
> NoneType
>
> Any help is appreciated, thanks!
>
Any comments? Am I asking the right question? Basically I have a simple C++
type and want to extend it to python. However, I haven't figured out a way to
do the C++ to python conversion with boost python's to_python/from_python
converter scheme. Am I missing something?
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