Secret Recipes of the Python Ninja

Implementing ChainMap

ChainMap is a dictionary-like class, used to create a single view of multiple mappings. It allows for quick linking between multiple mappings so they can all be considered as a single unit, which is useful when simulating nested scopes and when templating. This can be faster than creating a new dictionary and running update() calls repeatedly.

The command to create a ChainMap is as follows:

collections.ChainMap(*maps)

As usual, the *maps is simply a number of dictionaries or other map objects passed in to be combined into a single, updateable view. If no mappings are passed in, then an empty dictionary is created so the new chain has at least one mapping available to it.

The mappings themselves are contained, behind ...