[Python-Dev] Type/class

[Guido van Rossum]

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/)