Dictionary Mixin Framework

This script makes it easy to provide a full dictionary interface to a class defining only a few mapping methods for getting, setting, deleting, and listing keys.

Also, a function is provided to incorporate the mixin at runtime so that code for existing modules need not be modified.

By usmodules nixin as a superclass, you are free to overwrite any of these methods with your own and not break the mixin. For instance, your class may already define the .get() method but not any of the iter functions.

The reason for implementing the full dictionary interface is to maximize substitutability. Given code that was designed to work with a dictionary, an object of your class (with the mixin) can be substituted for the dictionary.

Some modules like shelve implement a subset of the dictionary interface. If you want to substitute a persistent shelve for a dictionary in existing code, then its interface needs to be broadened to handle all of the dictionary methods.