Python data structure for a collection of objects with random access based on an attribute

Question

I need a collection of objects which can be looked up by a certain (unique) attribute common to each of the objects. Right now I am using a dicitionary assigning the dictionary

Answer 1

Editing to correct the problem I had - which was due to my "collection = dict()" default parameter (*bonk*). Now, each call to the function will return a class with its own collection as intended - this for convenience in case more than one such collection should be needed. Also am putting the collection in the class and just returning the class instead of the two separately in a tuple as before. (Leaving the default container here as dict(), but that could be changed to Alex's WeakValueDictionary, which is of course very cool.)

def make_item_collection(container = None):
    ''' Create a class designed to be collected in a specific collection. '''
    container = dict() if container is None else container
    class CollectedItem(object):
        collection = container
        def __init__(self, key, title=None):
            self.key = key
            CollectedItem.collection[key] = self
            self.title = title
        def update_key(self, new_key):
            CollectedItem.collection[
                new_key] = CollectedItem.collection.pop(self.key)
            self.key = new_key
    return CollectedItem

# Usage Demo...

Item = make_item_collection()
my_collection = Item.collection

item_instance_1 = Item("unique_key1", title="foo1")
item_instance_2 = Item("unique_key2", title="foo2")
item_instance_3 = Item("unique_key3", title="foo3")

for k,v in my_collection.iteritems():
    print k, v.title

item_instance_1.update_key("new_unique_key")

print '****'
for k,v in my_collection.iteritems():
    print k, v.title

And here's the output in Python 2.5.2:

unique_key1 foo1
unique_key2 foo2
unique_key3 foo3
****
new_unique_key foo1
unique_key2 foo2
unique_key3 foo3