Data structure to implement a dictionary with multiple indexes?

Question

I am looking for a data structure that holds the same values under two different indexes, where I can access the data by either one.

Exampl

Answer 1

Just use three maps.

maps = [dict(), dict(), dict()]

def insert(rec):
   maps[0][rec[0]] = rec
   maps[1][rec[1]] = rec
   maps[2][rec[2]] = rec

Changes to key attributes of the rec object will require reinsertion though. Just like any other map, when you change the key of an object.

The maps just map key -> object, after all. They don't actually store copies of the object (it just isn't garbage collected). So a map is an index, nothing more. If you want three indexes, use three maps. Write a couple of glue code functions to manage them.

As mentioned by Trevor, you can also use a shared dictionary:

index = dict()

def insert(rec):
    index[rec[0]] = rec
    index[rec[1]] = rec
    index[rec[2]] = rec

then you can access it by either.

Beware of key collisions though!