Create a PyObject with a pointer to a C function

Question

Let's say I have this Python function:

def foo(bar):
    bar()

And this C function

void bar() {
}

How can I create a PyObject with Python C API that holds a pointer to bar function so I can call the Python function. Something like this

PyObject* function = PyObject_GetAttrString(module, "foo");
// how to create PyObject* args?
PyObject* result = PyObject_Call(function, args, NULL);

Searched and read the docs, but can not find a similar example

You can use PyCFunction (create it with PyCFunction_New) - you may need to wrap your "raw" C function with something that has the appropriate signature (accepting PyObject*). That's less convenient if you need it to be dynamic though, because you need to worry about the lifetime of the PyMethodDef then — DavidW
– DavidW, Commented Jul 27, 2024 at 18:54

Marko Devcic · Accepted Answer · 2024-07-29 14:17:08Z

0

Thanks to DavidW for the hint, here is a working example how to set a void bar method with no parameters defined is some Python module

static PyObject* bar(PyObject* self, PyObject* args)
{
    return PyNone;
}

static PyMethodDef bar_func_def = {
    "bar",
    bar,
    METH_NOARGS,
    "docstrings go here"
};

PyObject* function_arg = PyCFunction_NewEx(&bar_func_def, pymodule, PyUnicode_FromString("pymodule"));
PyObject_SetAttrString(pymodule, "bar", function_arg );

answered Jul 29, 2024 at 14:17

Marko Devcic

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