I have found the solution to my problem. The base class of the user-defined c++ python extension type provides a static bool check( PyObject* ) method that checks whether the object is of its kind. // somewhere : class MyExtensionType : public Py::PythonExtension<MyExtensionType> { ... } //somewhere else Object someFunctionExposedToPython(const Tuple &a) { Object o = a[0]; if(MyExtensionType::check(o.ptr())) { MyExtensionType* cppObj = static_cast<MyExtensionType*>(cppObj); // do something with cppObj } else { // it's not a MyExtensionType*, do something else } } (of course this isn't needed for MyExtensionType methods where "this" is automatically set correctly) this is exactly what i needed. hope this can help someone else (although it seems everyone here uses boost :) Benjamin -----Message d'origine----- De : c++-sig-bounces@python.org [mailto:c++-sig-bounces@python.org] De la part de Benjamin Golinvaux Envoyé : Saturday, August 28, 2004 11:48 PM À : Development of Python/C++ integration Objet : [C++-sig] CXX : getting a C++ object Hello I would like to wrap a small C++ library using CXX. I would like to know how I can extract the C++ instance from a PyObject passed to a function. Can I assume, after a correct type check, that I can safely downcast the PyObject ? (or using dynamic_cast ?) If I can't (or don't want to) use dynamic_cast , what could then be the best way to test that a PyObject is actually from a wrapped C++ "python type" class ? (sorry I'm a beginner in the Python C API) Thanks for your help Benjamin Golinvaux -------------------------------------------------------- The information contained in this message or any of its attachments may be privileged and confidential and intended for the exclusive use of the addressee. If you are not the addressee any disclosure, reproduction, distribution or other dissemination or use of this communication is strictly prohibited. If you have received this transmission by error please notify the sender immediately and then delete this email. EURESYS shall not be liable for any loss of or damage to revenues, profits, goodwill, data, information systems or other special, incidental, indirect, consequential or punitive damages of any kind arising in connection with the use of information contained in this mail or its attachments. Email transmission cannot be guaranteed to be secure or error free as information could be intercepted, corrupted, lost, destroyed, arrive late or incomplete, or contain viruses. The sender therefore is in no way liable for any errors or omissions in the content of this message, which may arise as a result of email transmission. If verification is required, please request a hard copy. Please note that neither EURESYS, nor the sender accepts any responsibility for viruses and it is your responsibility to scan attachments (if any). -------------------------------------------------------- _______________________________________________ C++-sig mailing list C++-sig@python.org http://mail.python.org/mailman/listinfo/c++-sig -------------------------------------------------------- The information contained in this message or any of its attachments may be privileged and confidential and intended for the exclusive use of the addressee. If you are not the addressee any disclosure, reproduction, distribution or other dissemination or use of this communication is strictly prohibited. If you have received this transmission by error please notify the sender immediately and then delete this email. EURESYS shall not be liable for any loss of or damage to revenues, profits, goodwill, data, information systems or other special, incidental, indirect, consequential or punitive damages of any kind arising in connection with the use of information contained in this mail or its attachments. Email transmission cannot be guaranteed to be secure or error free as information could be intercepted, corrupted, lost, destroyed, arrive late or incomplete, or contain viruses. The sender therefore is in no way liable for any errors or omissions in the content of this message, which may arise as a result of email transmission. If verification is required, please request a hard copy. Please note that neither EURESYS, nor the sender accepts any responsibility for viruses and it is your responsibility to scan attachments (if any). --------------------------------------------------------