Josh Haberman <[email protected]> added the comment:
> You can also call (PyObject_Call*) the metaclass with (name, bases,
> namespace);
But won't that just call my metaclass's tp_new? I'm trying to do this from my
metaclass's tp_new, so I can customize the class creation process. Then Python
code can use my metaclass to construct classes normally.
> I wouldn't recommend [setting ob_type] after PyType_Ready is called.
Why not? What bad things will happen? It seems to be working so far.
Setting ob_type directly actually solves another problem that I had been having
with the limited API. I want to implement tp_getattro on the metaclass, but I
want to first delegate to PyType.tp_getattro to return any entry that may be
present in the type's tp_dict. With the full API I could call
self->ob_type->tp_base->tp_getattro() do to the equivalent of super(), but with
the limited API I can't access type->tp_getattro (and PyType_GetSlot() can't be
used on non-heap types).
I find that this does what I want:
PyTypeObject *saved_type = self->ob_type;
self->ob_type = &PyType_Type;
PyObject *ret = PyObject_GetAttr(self, name);
self->ob_type = saved_type;
Previously I had tried:
PyObject *super = PyObject_CallFunction((PyObject *)&PySuper_Type, "OO",
self->ob_type, self);
PyObject *ret = PyObject_GetAttr(super, name);
Py_DECREF(super);
But for some reason this didn't work.
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<https://bugs.python.org/issue15870>
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