[C++-sig] boost.python: modifying class getattr (original) (raw)

Hans Meine meine at kogs1.informatik.uni-hamburg.de
Mon Dec 5 17:47:11 CET 2005

On Wednesday 16 November 2005 18:37, David Abrahams wrote:

> is there a way to modify the type object associated with Foo instances > so that instead of calling PyObjectGenericGetAttr when an attribute is > requested, Python calls a function > PyObject * > FooGetAttr(PyObject *obj, PyObject *name) > ?

PyTypeObject* Foot = (PyTypeObject*)Foo.ptr(); Foot->tpgetattro = FooGetAttr;

Interesting. In a desperate attempt to make accessing (2-dimensional) point elements from my Polygon class faster (a native python list of these objects is twice as fast), I tried to manually set (PyTypeObject*)Foo_.ptr() ->tp_as_sequence->sq_item to my hand-crafted getitem implementation... which made it slower. ;-)

Obviously, my getitem using extract(self)() is doing an extra type-checking which my previously used boost::python function did not do (since boost knew that self contained my object), and - I should have had a little more confidence in the power of boost::python - was already registered in the special tp_as_sequence->sq_item slot (which triggered an assert I had put in before overwriting sq_item). ;-}

That's cool. What a pity that I spent my afternoon trying to optimize where it was already done optimally. ;-/

Obviously, the only remaining advantage of a python list is that it contains readily-wrapped python objects that can simply be returned (after an incref())?!

-- Ciao, / / /--/ / / ANS

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