Mastering Object-oriented Python

Designing an access layer for shelve

Here's how shelve might be used by an application. We'll look at parts of an application that edits and saves microblog posts. We'll break the application into two tiers: the application tier and the data tier. Within an application tier, we'll distinguish between two layers:

• Application processing: These objects are not persistent. These classes will embody the behavior of the application as a whole. These classes respond to the user selection of commands, menu items, buttons, and other processing elements.
• Problem domain data model: These are the objects that will get written to a shelf. These objects embody the state of the application as a whole.

The definitions of blog and post shown previously have no formal ...