Python C API Example

main.cpp

#include <Python.h>

static PyObject* increment(PyObject* self, PyObject* args)
{
	double value, unused;

	if (!PyArg_ParseTuple(args, "dd", &value, &unused))
		return NULL;

	value += 42;

	return Py_BuildValue("d", value);
}

static PyObject* add_len(PyObject* self, PyObject* args)
{
	PyObject* arg;

	if (!PyArg_ParseTuple(args, "O", &arg))
		return NULL;

	int len = PyDict_Size(arg);
	PyDict_SetItemString(arg, "length", Py_BuildValue("i", len));

	return arg;
}

static PyMethodDef PyCApiMethods[] =
{
	{ "increment", increment, METH_VARARGS, "increment a number" },
	{ "add_len", add_len, METH_VARARGS, "add the length of a dict to the dict" },
	{ NULL, NULL, 0, NULL }
};

static struct PyModuleDef clientmodule = {
	PyModuleDef_HEAD_INIT,
	"pycapi",   /* name of module */
	"documentation goes here", /* module documentation, may be NULL */
	-1,       /* size of per-interpreter state of the module,
			  or -1 if the module keeps state in global variables. */
    PyCApiMethods,
};

PyMODINIT_FUNC PyInit_pycapi(void)
{
	return PyModule_Create(&clientmodule);
}