There's a very good tutorial on writing from/to python converters. This tutorial was suggested to me by one of the members of this mailing list and I've found it very useful.
The link is this one: http://misspent.wordpress.com/2009/09/27/how-to-write-boost-python-converters/ After reading this very useful article, I managed to write my mds-utils library (the link is at the end of this e-mail) which you can download to see how you can write a from/to python converter. Bye. Michele 2010/5/25 X Wang <wangx0...@yahoo.com>: > >> 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? > > > > _______________________________________________ > Cplusplus-sig mailing list > Cplusplus-sig@python.org > http://mail.python.org/mailman/listinfo/cplusplus-sig > -- Michele De Stefano http://www.linkedin.com/in/micdestefano http://code.google.com/p/mds-utils http://xoomer.virgilio.it/michele_de_stefano _______________________________________________ Cplusplus-sig mailing list Cplusplus-sig@python.org http://mail.python.org/mailman/listinfo/cplusplus-sig
