Duncan Booth wrote: DB> I figured out what is going on in the code to deallocate an old-style class DB> instance: DB> DB> The reference count is temporarily incremented. DB> DB> If the class has a __del__ method then a descriptor is created for the DB> method and called. When the call returns, the descriptor is released. DB> DB> Then the object itself is released using special code to avoid a recursive DB> call to the deallocator. DB> DB> However, if the trashcan mechanism is invoked by the attempt to release the DB> descriptor, it actually queues the descriptor in the trashcan. Since the DB> descriptor contains a reference to the object it has effectively DB> resurrected it. This means the special code to avoid the recursive call DB> simply decrements the reference count but does not release anything (the DB> object has been resurrected by the descriptor). When the descriptor is DB> later released the __del__ method is triggered a second time.
Thank You for so detailed explanation! -- GMT More Then ... -- http://mail.python.org/mailman/listinfo/python-list
