[Python-Dev] instancemethod_getattro seems to be partially wrong

Christian Tismer tismer at tismer.com
Mon Nov 17 23:05:02 EST 2003

Hi again, again!

After hours of investigating why my instance method __reduce__
doesn't work, I found out the following:


does this:

	if (PyType_HasFeature(tp, Py_TPFLAGS_HAVE_CLASS)) {
		if (tp->tp_dict == NULL) {
			if (PyType_Ready(tp) < 0)
				return NULL;
		descr = _PyType_Lookup(tp, name);

	f = NULL;
	if (descr != NULL) {
		f = TP_DESCR_GET(descr->ob_type);
		if (f != NULL && PyDescr_IsData(descr))
			return f(descr, obj, (PyObject *)obj->ob_type);

Why, please can someone explain, why does it ask for
PyDescr_IsData ???
I think this is wrong.
I'm defining an __reduce__ method, and it doesn't provide
a tp_descr_set, as defined in...

PyDescr_IsData(PyObject *d)
	return d->ob_type->tp_descr_set != NULL;

but for what reason is this required???

This thingie is going wrong both in Py 2.2.3 and in Py 2.3.2,
so I guess there is something very basically going wrong.
I'd like to fix that, but I need to understand what the intent of
this code has been.

Can somebody, perhaps the author, explain why this is this way?

thanks so much -- chris

Christian Tismer             :^)   <mailto:tismer at tismer.com>
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