[Python-3000] Ctypes as cross-interpreter C calling interface (original) (raw)

Paul Prescod paul at prescod.net
Mon Aug 14 22:00:59 CEST 2006

On 8/14/06, Guido van Rossum <guido at python.org> wrote:

The major difference between all these examples and ctypes is that ctypes has no way of introspecting the wrapped library; you have to repeat everything you know about the API in your calls to ctypes (and as was just shown in another thread about 64-bit issues, that's not always easy).

An excellent point and very clarifying (though I still don't totally understand the relationship with Parrot).

What do you think about techniques like these:

I agree that this is an issue.

But then on the other hand, given N methods and objects that you need wrapped, you will in general need to make N individual mapping statements no matter what technology you use. The question is how many lines of mapping are you doing? Ctypes currently requires you to re-declare what you know about the C library. Hand-written C libraries require you to do go through other hoops.

For example, looking at Pygame ctypes, consider the following method:

def __copy__(self):
    return Rect(self.x, self.y, self.w, self.h)

That's the ctypes version. Here's the C version:

/* for copy module / static PyObject rect_copy(PyObject* oself, PyObject* args) { PyRectObject* self = (PyRectObject*)oself; return PyRect_New4(self->r.x, self->r.y, self->r.w, self->r.h); }

static struct PyMethodDef rect_methods[] = { ... {"copy", (PyCFunction)rect_copy, 0, NULL},... };

So there is some repetition there as well (casts, function name duplications, etc.).

Paul Prescod -------------- next part -------------- An HTML attachment was scrubbed... URL: http://mail.python.org/pipermail/python-3000/attachments/20060814/a281094f/attachment.htm

More information about the Python-3000 mailing list