[aewens]

You may be thinking of the `frozenset()` built in or the third party Python module [frozendict](https://pypi.org/project/frozendict/)?

Personally, I’ve been using a wrapper around `collections.namedtuple` as an underlying data structure to create frozen dictionaries when I’ve needed something like that for a project.

[guidopallemans]

When you are making str -> Any dictionaries it's quite likely you're better off with dataclasses or namedtuples anyway.

[TheFlyingFish]

That works if you're dealing with a known set of keys (i.e. what most statically-typed languages would call a struct). It falls down if you need something where the keys are unknowable until runtime, like a lookup table.

I do like dataclasses, though. I find them sneaking into my code more and more as time goes on. Having a declared set of properties is really useful, and it doesn't hurt either that they're syntactically nicer to use.