[Python-Dev] Type/class (original) (raw)

Guido van Rossum guido@digicool.com
Thu, 10 May 2001 19:03:13 -0500

Glad somebody is watching what I'm doing here -- I was afraid I was having too much fun by myself! :-)

-------- Original Message -------- Log Message:

Make attributes of subtypes writable, but only for dynamic subtypes derived in Python using a class statement; static subtypes derived in C still have read-only attributes. -------- Original Message -------- I would like to argue that "plain old C types" should act as if they _have dict_s for consistency with other types.

Good point. Plain old types currently (in the descr-branch) have a readonly dict (using a proxy) and no settable attributes. I will probably give types settable attributes in a next revision, but I prefer not to make the type's dict writable -- I need to be able to watch the setattr calls so that if someone changes DictType.getitem I can change the mp_subscript to a C function that calls the getitem method. For speed reasons, if you don't override them, the C tp_slot functions carry out the operation directly, and the slot methods call the C tp_slot functions; but when slot is overridden, tp_slot must call slot.

It is sometimes useful to be able to annotate objects by adding attributes to them. But this only works with class instance objects, not instances of types.

Paul Prescod

If you're talking about instances: instances of subtypes of built-in types have a dict of their own to which you can add stuff to your heart's content. Instances of built-in types will continue not to have a dict (it would cost too much space if every object had a dict, even if it was a NULL pointer when no attrs are defined).

If you mean you want to annotate types like you can annotate classes, that should be possible once I implement what I describe above.

--Guido van Rossum (home page: http://www.python.org/~guido/)