Extending Python 3 with C++

Question

I'm trying to extend Python 3 using instructions given here and I'm fairly confident I've followed the instructions correctly so far, but it asks me to include this code:

PyMODINIT_FUNC
PyInit_spam(void)
{
    PyObject *m;

    m = PyModule_Create(&spammodule);
    if (m == NULL)
        return NULL;

    SpamError = PyErr_NewException("spam.error", NULL, NULL);
    Py_INCREF(SpamError);
    PyModule_AddObject(m, "error", SpamError);
    return m;
}

I'm writing this in MSVC++ 2010 and it's warning me that &spammodule is undefined (the name of the module is spammodule.cpp), but it doesn't define it anywhere in the instructions so I assume that it should recognise it automatically as the name of the module.

The full code is:

#include <Python.h>
#include <iostream>
using namespace std;

static PyObject *SpamError;

int main()
{
    cout << "Test" << endl;
    system("PAUSE");
    return(0);
}

static PyObject *spam_system(PyObject *self, PyObject *args)
{
    const char *command;
    int sts;

    if (!PyArg_ParseTuple(args, "s", &command))
        return NULL;
    sts = system(command);
    return PyLong_FromLong(sts);
}

PyMODINIT_FUNC
PyInit_spam(void)
{
    PyObject *m;

    m = PyModule_Create(&spammodule);
    if (m == NULL)
        return NULL;

    SpamError = PyErr_NewException("spam.error", NULL, NULL);
    Py_INCREF(SpamError);
    PyModule_AddObject(m, "error", SpamError);
    return m;
}

There are no such things as modules in C++. You'll probably want to start over and read a good C++ book before continuing, you'll save yourself a lot of frustration. — Seth Carnegie
– Seth Carnegie, Commented Feb 24, 2012 at 23:41
@SethCarnegie, he's using the Python C API, so The C Programming Language (2nd ed.) should be sufficient. — Matthew Flaschen
– Matthew Flaschen, Commented Feb 24, 2012 at 23:43
I'll be studying C++ next term at university, though I'm under time constraints to finish a project in Python at the moment, so I don't have much time to learn C++, but thanks. — Tagc
– Tagc, Commented Feb 24, 2012 at 23:54

Matthew Flaschen · Accepted Answer · 2012-02-24 23:39:17Z

2

You're still writing C++, so you still need to declare spammodule somewhere. This is given later on the same page:

static struct PyModuleDef spammodule = {
   PyModuleDef_HEAD_INIT,
   "spam",   /* name of module */
   spam_doc, /* module documentation, may be NULL */
   -1,       /* size of per-interpreter state of the module,
                or -1 if the module keeps state in global variables. */
   SpamMethods
};

answered Feb 24, 2012 at 23:39

Matthew Flaschen

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Comments

Taryn · Accepted Answer · 2014-06-05 11:39:18Z

1

No no no, PyModule_Create() accepts a pointer to the module definition structure and has absolutely nothing to do with the name of the source file.

edited Jun 5, 2014 at 11:39

Taryn

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answered Feb 24, 2012 at 23:39

user405725

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