May 31, 2004
7:56 a.m.
Raymond Hettinger wrote:
Instances of classes inheriting from str, tuple, etc cannot be weakly referenced. Does anyone know the reason for this?
In addition to the reason Christian gave, one (conceptually more important) reason is that strings can't participate in cycles. Weak references were introduced as a mechanism to avoid creating cyclic structures, so that "backward" links could be made weak references. It appears that people have then been eager to add weakref support to other datatypes. IMO, they have been too eager. For example, I can't see a reason why Unicode objects should be weakly referencable (just as I can't see a reason for plain strings). Regards, Martin