A “frozen” dictionary for Python

This is a type that I would use a lot.

For example, I often write classes that do cacheable analysis that results in a dict (e.g. the class stores a list of tiles defined by points and users want a point-to-tiles mapping for convenience). It's worth caching those transformations, e.g. using @functools.cached_property, but this introduces a risk where any caller could ruin the returned cached value by editing it. Currently, I take the safety hit (cache a dict) instead of the performance hit (make a new copy for each caller). Caching a frozendict would be a better tradeoff.

Maybe you should take a look at pyrsistent. That allows you to make frozen “maps”. You can “evolve” them into new versions of the objects and it keeps the references to the unchanged keys and values under the hood so it’s fast and memory efficient.