Partitioned Collections in SQLAlchemy
Jason Kirtland discusses some advanced usage of SQLAlchemy's collections framework: Storing a Dictionary of Lists, which he terms a "Partitioned Collection". A "collection" in that the ultimate storage is a single series of items, "partitioned" in that each item contains a discriminator of some kind which allows the monolithic collection to be further grouped into two levels of collection. A very detailed introduction to how SQLA approaches collections.