Python C++ API function with multiple arguments

Question

I'm trying to create a python module using my C++ code and I want to declare a function with multiple arguments. (3 in this case) I've read the docs and it says that I must declare METH_VARARGS which I did, but I think I also must change something inside my function to actually receive the arguments. Otherwise it gives me "too many arguments" error when I use my function in python.

Here is the code snippet I'm using:

...
// This function can be called inside a python file.
static PyObject *
call_opencl(PyObject *self, PyObject *args)
{
    const char *command;
    int sts;

    // We except at least one argument to this function
    // Not sure how to accept more than one.
    if (!PyArg_ParseTuple(args, "s", &command))
        return NULL;

    OpenCL kernel = OpenCL();
    kernel.init();

    std::cout << "This message is called from our C code: " << std::string(command) << std::endl;

    sts = 21;

    return PyLong_FromLong(sts);
}

static PyMethodDef NervebloxMethods[] = {
    {"call_kernel",          call_opencl,         METH_VARARGS,              "Creates an opencv instance."},
    {NULL, NULL, 0, NULL}        /* Sentinel */
};

...

Ahmed AEK · Accepted Answer · 2022-11-28 09:44:23Z

2

You are still expecting one argument.

if (!PyArg_ParseTuple(args, "s", &command))

the documentation defines how you can expect optional or additional arguments, for example "s|dd" will expect a string and two optional numbers, you still have to pass two doubles to the function for when the numbers are available.

double a = 0; // initial value
double b = 0;
if (!PyArg_ParseTuple(args, "s|dd", &command, &a, &b))

edited Nov 28, 2022 at 9:44

answered Nov 28, 2022 at 7:50

Ahmed AEK

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