[Python-Dev] Why aren't more things weak referencable

[Delaney, Timothy C (Timothy)]

Guido van Rossum wrote:

>> For strings at least, perhaps it is time to bite the bullet and
>> include weak reference support directly.  Weak reference support ups
>> the per string memory overhead from five words (ob_type, ob_refcnt,
>> ob_size, ob_shash, ob_sstate) to six.  The whole concept of weak
>> dictionaries is much more useful when strings can be used as keys
>> and/or values.
> 
> Hmm... it is a high price to pay to add another word (*and* some extra
> code at dealloc time!) to every string object when very few apps need
> them and strings are about the most common data type.  And since
> they're immutable, what's the point of having weak refs to strings in
> the first place?  (Note that the original poster asked about
> *subclasses* of strings.)

Perhaps there should be a standard weakly-referenceable proxy whose sole
purpose in life would be to wrap objects that can't be directly weakly
referenced. Kind of the opposite of ProxyTypes - it would have an
internal strong reference to the object.

This could be done transparently as well - if creating an instance of
ReferenceType would raise a TypeError, we take a hit and wrap the
object.

Tim Delaney