index all instances by id - a memory leak?

[Dan Barbus]

Hi all,

I'm a python beginner, and I have a problem with no solution I can
see:

I want to index all instances of an object by an internal id (not the
hash) and be able to retrieve them later.

I created a class-level dictionary (Item._itemById) where I add every
new instance. My problem is:

How do I delete the instances when the class is no longer in use?
( having it in a map makes it 'in use' all the time, so my
implementation results in a memory leak :( ).

Here's the code:

class Item():
    """This is the base class for all data items"""

    _idBase = None
    _count = 0
    _itemsById = {}

    def __init__(self, title = ''):
        Item._count += 1
        self.id = Item._generateId(self)
        Item._itemsById[self.id] = self
        self.title = title

    def __del__(self):
        Item._count -= 1
        # Should I do something here to delete the instance?
        # Will this ever be called if the instance is in a static
dictionary?

    def _generateId(self):
        """Generates an unique id for the instance. The id will be
unique
        for both the current run and all runs in general.

        """
        if not Item._idBase:
            Item._idBase = str(hash(self))
        return Item._idBase + '-' + str(Item._count).zfill(6)

    def getItemById(id):
        return _itemsById[id]