On 06/24/2010 07:32 PM, Yongning Zhu wrote:

Hi,

I am following a tutorial to expose a custom iterator to python, The iterator was used in C++ by for(T_ITERATOR it();it.Valid();it.Next()){ T_VALUE v=it.Value(); }

And I wrote the following wrapper:

template<class Klass, class KlassIter> struct iterator_wrappers { static Klass next(KlassIter& o) { o.Next(); Klass result = o.Value(); if (!o.Valid()) { PyErr_SetString(PyExc_StopIteration, "No more data."); boost::python::throw_error_already_set(); } return result; }

static void wrap(const char* python_name) { //using namespace boost::python; class_<KlassIter>(python_name, init<>())//no_init .def("next", next) .def("__iter__", pass_through) ; } };

and expose it by iterator_wrappers<T_VALUE,T_ITERATOR>().wrap("t_iterator");

It compiles but when I am importing the module in python, there is an error saying:

python: ../../../../libs/python/src/converter/registry.cpp:212: void boost::python::converter::registry::insert(PyObject* (*)(const void*), boost::python::type_info, const PyTypeObject* (*)()): Assertion `slot->m_to_python == 0' failed. Aborted

Just a guess...is there any chance you might be exposing the same C++ iterator to Python multiple times? Admittedly, I've usually seen that produce warnings rather than assertion failures, but both cases seem to be related to Boost.Python not being particularly happy about having multiple to-python converters for a single C++ type. By the way, you might have more luck with Boost.Python questions at the cplusplus-sig@python.org list. HTH Jim Bosch