dict_collapse.py

def main():
    # this is the dict that we want to trim down.
    # basically we want to collapse `foo` into a list for a common `id`
    bloated_map = [{'foo': 2, 'id': 160},
        {'foo': 314, 'id': 160},
        {'foo': 314, 'id': 161},
        {'foo': 2, 'id': 161}]

    # this gives us a list of unique ids
    id_list = set([x['id'] for x in bloated_map])

    # this is going to hold our ouput
    slim_map = []

    # loop through unique ids
    for i in id_list:
        # make  a list of foos associated with id `i`
        foos = [x['foo'] for x in bloated_map if x['id'] == i]
        slim_map.append({'id': i, 'foos': foos})

    print slim_map


if __name__ == '__main__':
    main()