(No luck on C++-sig - is that list even active? There's absolutely no traffic, not one mail in two days. Anyway, trying again here.) Hi, I've got a hand-wrapped plugin interface hierarchy for my program allowing implementing plugins in Python. This looks approximately like this: class Plugin { public: virtual void init() = 0; virtual PluginCategory getCategory() = 0; // Subtype of the plugin // ... }; class InputPlugin : public Plugin { public: virtual void loadData(const string &resource, DataBag &target) = 0; }; class OutputPlugin : public Plugin { public: virtual void saveData(const string &resource, const DataBag &source) = 0; }; These are the plugin interfaces. PluginCategory is an enum identifying the concrete subtype of the plugin, i.e. either Input or Output. I've got them wrapped like this: class PluginWrap : public Plugin, public boost::python::wrapper<Plugin> { virtual void init() { this->get_override("init")(); } // ... }; class InputPlugin : public InputPlugin, public boost::python::wrapper<InputPlugin> { virtual void loadData(...) { ... } }; // ... BOOST_PYTHON_MODULE(myprogram) { class_("Plugin") .def("init", pure_virtual(&Plugin::init)) .def( ... ) ; class_("InputPlugin") .def("loadData", ...) ; // ... } A plugin file looks like this: from myprogram import * class SomePlugin(InputPlugin): def init(self): // ... // ... plugins = [SomePlugin()] I then attempt to load these modules like this: PythonLoader::load(const path &file) { // Parse file and get namespace object for it. Get the "plugins" list and extract a python::list. Get the length of that list. python::list plugs = ...; int len = // get length of plugs for(int i = 0; i < len; ++i) { try { py::object plug = plugs[i]; Plugin *plugin = py::extract(plug); // <------------- plugins.push_back(plugin); } catch(py::error_already_set &e) { // handle error } } } Finally, my problem: the extract call fails: TypeError: No registered converter was able to extract a C++ pointer to type Plugin from this Python object of type SomePlugin So here are my questions: 1) Is this expected behaviour? Does my wrapping not register the appropriate base pointer extractors? 2) How can I manually register appropriate converters? 3) If 2 is not possible, how can I work around the problem? Thanks in advance Sebastian Redl