generator.py

def uniques(source, fmap=lambda x: x, restrictOn=lambda x: x):
    """Map a function over an iterable, and yield elements which are
    unique according to the given restriction function.

    An exception raised in the mapping or restriction function causes
    that element to be silently skipped.
    """

    seen = set()
    for thing in source:
        try:
            thing = fmap(thing)

            if restrictOn(thing) in seen:
                continue
            seen.add(restrictOn(thing))

            yield thing
        except:
            continue

# example usage:

# with open(jsonfile) as f:
#     data = json.load(f)
#     for fields in functions.uniques(
#             data['hits']['hits'],
#             fmap=lambda hit: hit['_source']['@fields'],
#             restrictOn=lambda fields: fields['path']):