connect.py

def connect(*args):
    maps = list()
    for collection, keyGetter in args:
        m = dict()
        for item in collection:
            key = keyGetter(item)
            m[key] = item
        maps.append(m)

    result = list()
    resultKeys = set()
    for collection, keyGetter in args:
        for item in collection:
            key = keyGetter(item)
            if key in resultKeys:
                continue
            resultKeys.add(key)
            result.append(tuple(m.get(key) for m in maps))

    return result


def test_connect():
    from pprint import pprint, pformat
    collA = [
        {"id": 123, "name": "Hello"},
        {"id": 456, "name": "Foo"},
    ]
    collB = [
        {"id": 456, "data": "def"},
        {"id": 123, "data": "abc"},
    ]
    result = connect(
        (collA, lambda x: x["id"]),
        (collB, lambda x: x["id"]))
    assert result == [
        ({"id": 123, "name": "Hello"}, {"id": 123, "data": "abc"}),
        ({"id": 456, "name": "Foo"},   {"id": 456, "data": "def"}),
    ], pformat(result)

    groups = [
        {"groupId": 2, "name": "group 2"},
        {"groupId": 1, "name": "group 1"},
        {"groupId": 3, "name": "group 3"},
    ]
    ads = [
        {"groupId": 2, "ad": "some ad"},
    ]
    banners = [
        {"groupId": 3, "banner": "some banner"},
    ]
    result = connect(
        (groups,  lambda g: g["groupId"]),
        (ads,     lambda a: a["groupId"]),
        (banners, lambda b: b["groupId"]))
    assert result == [
        ({"groupId": 2, "name": "group 2"}, {"groupId": 2, "ad": "some ad"}, None),
        ({"groupId": 1, "name": "group 1"}, None, None),
        ({"groupId": 3, "name": "group 3"}, None, {"groupId": 3, "banner": "some banner"}),
    ], pformat(result)


if __name__ == "__main__":
    test_connect()