This is a tree which contains prefixes of names.

this_is_usable_code.py

    # Lets build a dictionary of people, like this:
    names = [u'{} {}'.format(f.lower(),e.lower()) for (f,e) in Participant.objects.values_list('fname', 'ename').order_by('fname', 'ename')]
    autocompletion_tree = defaultdict(list)
    for (i,n) in enumerate(names):
        s = ''
        for c in n:
            s += c
            autocompletion_tree[s].append(i)

    # Purge it!
    # Make it smaller!
    for n in names:
        for x in range(2, len(n)+1):
            if len(autocompletion_tree[n[:x]]) < 2:
                del autocompletion_tree[n[:x]]

    autocompletion_json  = json.dumps(autocompletion_tree)
    autocompletion_names = json.dumps(names)