Modern Python Standard Library Cookbook

How it works...

As we already know from the previous recipe, ChainMap looks up keys in all the provided dictionaries, so it's like the sum of all the dictionaries. The unpacking operator (**) works by inviting all keys to the container and then providing an argument for each key.

As ChainMap has keys resulting from the sum of all the provided dictionaries keys, it will provide the keys contained in all the dictionaries to the unpacking operator, thus allowing us to provide keyword arguments from multiple dictionaries.