Python Data Structures and Algorithms

ChainMaps

The collections.chainmap class was added in Python 3.2 and it provides a way to link a number of dictionaries, or other mappings, so that they can be treated as one object. In addition, there is a maps attribute, a new_child() method, and a parents property. The underlying mappings for ChainMap objects are stored in a list and are accessible using the maps[i] attribute to retrieve the ith dictionary. Note that even though dictionaries themselves are unordered, ChainMaps are an ordered list of dictionaries. ChainMap is useful in applications where we are using a number of dictionaries containing related data. The consuming application expects data in terms of a priority, where the same key in two dictionaries is given priority if ...