Summary
We've seen the basics of how to use the shelve module. This includes creating a shelf and designing keys to access the objects we've placed in the shelf. We've also seen the need for an access layer to perform the lower-level CRUD operations on the shelf. The idea is that we need to distinguish between the class definitions that are focused on our application and other administrative details that support persistence.
Design considerations and trade-offs
One of the strengths of the shelve module is allowing us to persist distinct items. This imposes a design burden to identify the proper granularity of the items. Too fine a granularity and we waste time assembling containers from their pieces. Too coarse a granularity and we waste time fetching and storing items that aren't relevant.
Since a shelf requires a key, we must design appropriate keys for our objects. We must also manage the keys for our various objects. This means using additional attributes to store keys and possibly creating...
