Hello, I'm using weakrefs in a small multi-threaded application. I have been using object IDs as dictionary keys with weakrefs to execute removal code, and was glad to find out that this is in fact recommended practice (http://docs.python.org/library/weakref.html)
> This simple example shows how an application can use objects IDs to retrieve > objects that it has seen before. The IDs of the objects can then be used in > other > data structures without forcing the objects to remain alive, but the objects > can > still be retrieved by ID if they do. After reading this, I realized it made no explicit mention of thread safety in this section, whereas other sections made a note of correct practice with threads. The docs for the id() function specify > Return the identity of an object. This is guaranteed to be unique among > simultaneously existing objects. (Hint: it's the object's memory address.) While guaranteed unique for simultaneously existing objects, how often will an object assume an ID previously held by former object? Given that the ID is a memory address in Python's heap, I assume the answer is either not often, or very often. Specifically, I'm wondering if the case can occur that the callback for a weakref is executed after another object has been allocated with the same object identifier as a previous object. If such an object is inserted into a module-level dictionary, could it over-write a previous entry with the same identifier and then get deleted whenever the weakref callback happens to fire? On a related note, what is a recommended way to obtain a weak reference to a thread? -- http://mail.python.org/mailman/listinfo/python-list
