L.S. I am working on an extension that allows one to open Java .jar files and use the objects defined in it (via CNI or JNI) in Python. It works like a charm, but I am stuck with the definition of a metatype for the wrappers. I have to do this in Python now, with a helper class. I did find examples of how to define metatypes, but I can't find anything on how to declare one type using this metatype. Could anyone point me to examples or documentation or help me fix my code below? What I have is a type JObject that has a metatype JObjectMeta, but the objects created from it seem not properly initialized. If I call PyString_Str(self) in JObjectMeta_init, it seg faults. De Python code that initiates this is: class MyJObject(JObject): pass Below is the complete, contained code of the extension. Thanks in advance, Erik Groeneveld #include /*************** JObjectMeta *******************/ typedef struct { PyObject_HEAD } JObjectMeta; PyTypeObject JObjectMetaType = { PyObject_HEAD_INIT(NULL) }; int JObjectMeta_init(PyObject* self, PyObject* args, PyObject *kwargs) { printf("before str\n"); PyObject_Str(self); printf("after str\n"); return 0; } PyObject* JObjectMeta_getattro(PyObject *self, PyObject *name) { return PyBaseObject_Type.tp_getattro(self, name); } /*************** JObject ***********************/ typedef struct { PyObject_HEAD } JObject; PyTypeObject JObjectType = { PyObject_HEAD_INIT(&JObjectMetaType) }; int JObject_init(PyObject* self, PyObject* args, PyObject *kwargs) { return 0; } static PyMethodDef methods[] = { {NULL, NULL, 0, NULL} }; /*************** INIT *******************/ PyMODINIT_FUNC initmetaclass(void) { JObjectMetaType.tp_name = "metaclass.JObjectMeta"; JObjectMetaType.tp_basicsize = sizeof(JObjectMeta); JObjectMetaType.tp_flags = Py_TPFLAGS_DEFAULT; JObjectMetaType.tp_doc = "JObject objects"; JObjectMetaType.tp_init = JObjectMeta_init; JObjectMetaType.tp_base = &PyType_Type; // must ? JObjectMetaType.tp_new = PyType_GenericNew; JObjectMetaType.tp_getattro = JObjectMeta_getattro; JObjectType.tp_name = "metaclass.JObject"; JObjectType.tp_basicsize = sizeof(JObject); JObjectType.tp_flags = Py_TPFLAGS_DEFAULT|Py_TPFLAGS_BASETYPE; JObjectType.tp_doc = "JObjectMeta objects"; JObjectType.tp_init = JObject_init; JObjectType.tp_base = &JObjectMetaType; // must ? JObjectType.tp_new = PyType_GenericNew; PyObject* module = Py_InitModule3("metaclass", methods, "Metaclass try out."); if (module == NULL) { PyErr_Print(); exit(-1); } if (PyType_Ready(&JObjectMetaType) < 0) { PyErr_Print(); exit(-1); } if (PyModule_AddObject(module, "JObjectMeta", (PyObject*) &JObjectMetaType) < 0) { PyErr_Print(); exit(-1); } if (PyType_Ready(&JObjectType) < 0) { PyErr_Print(); exit(-1); } if (PyModule_AddObject(module, "JObject", (PyObject*) &JObjectType) < 0 ) { PyErr_Print(); exit(-1); } }