Passing a C pointer around with the Python/C API

Question

I\'m new to the Python/C API ... I\'m trying to add new functionality to my C program, wherein I can embed python into it and simultaneously extend functionality so that the

Answer 1

Assuming that you want some backwards compatibility, you want to use PyCObjects: http://docs.python.org/c-api/cobject.html

If you only want to use python 3, you can use a PyCapsule: http://docs.python.org/c-api/capsule.html

Basically the PyCObject stuff converts your opaque pointer into a PyObject that you can pass around within python and when you get back into C with one, you can unwrap it and use it.

PyCapsules are pretty similar except they add a few features, the main one being that they allow you to store multiple pointers in the Capsule, so it's basically a dict.

In your specific case, where you add the pointer, you'll just want to do this (error checking and destruction code removed):

PyObject *pystate = PyCObject_FromVoidPtr(State, NULL);
PyObject *dict = PyModule_GetDict(module);
PyDict_SetItemString(dict, "CStateObject", pystate);

# To retrieve it from self (assuming that it is an object)
PyObject *pystate = PyObject_GetAttrString(self, "CStateObject");
State *state = (State *)PyCObject_AsVoidPtr(pystate);