Why can't I extract a C++ type from a Python type using boost::python::extractor?
- by Robin
I've wrapped a C++ class using Py++ and everything is working great in Python. I can instantiate the c++ class, call methods, etc.
I'm now trying to embed some Python into a C++ application. This is also working fine for the most-part. I can call functions on a Python module, get return values, etc.
The python code I'm calling returns one of the classes that I wrapped:
import _myextension as myext
def run_script(arg):
my_cpp_class = myext.MyClass()
return my_cpp_class
I'm calling this function from C++ like this:
// ... excluding error checking, ref counting, etc. for brevity ...
PyObject *pModule, *pFunc, *pArgs, *pReturnValue;
Py_Initialize();
pModule = PyImport_Import(PyString_FromString("cpp_interface"));
pFunc = PyObject_GetAttrString(pModule, "run_script");
pArgs = PyTuple_New(1); PyTuple_SetItem(pArgs, 0, PyString_FromString("an arg"));
pReturnValue = PyObject_CallObject(pFunc, pArgs);
bp::extract< MyClass& > extractor(pReturnValue); // PROBLEM IS HERE
if (extractor.check()) { // This check is always false
MyClass& cls = extractor();
}
The problem is the extractor never actually extracts/converts the PyObject* to MyClass (i.e. extractor.check() is always false).
According to the docs this is the correct way to extract a wrapped C++ class.
I've tried returning basic data types (ints/floats/dicts) from the Python function and all of them are extracted properly.
Is there something I'm missing? Is there another way to get the data and cast to MyClass?
