Next step: Auto-inferring the correct (most narrow) TypedDict type from a frozendict. (Think `const foo = { … } as const` in TypeScript.) I miss this TS feature in Python on the daily.

Shoutout to pyrsistent, a personal favorite library for whenever I need to use lists, sets, or dicts as dict keys, or make sets of such items: https://github.com/tobgu/pyrsistent

A frozen dictionary would be very welcome. You can already do something similar using MappingProxyType [0]

  from types import MappingProxyType
  
  d = {}
  
  d["a"] = 1
  d["b"] = 2
  
  print(d)
  
  frozen = MappingProxyType(d)
  
  print(frozen["a"])
  
  # Error:
  frozen["b"] = "new"

[0]: https://docs.python.org/3/library/types.html#types.MappingPr...

If this gets wide enough use, they could add an optimization for code like this:

    n = 1000
    a = {}
    for i in range(n):
        a[i] = str(i)
    a = frozendict(a)  # O(n) operation can be turned to O(1)

It is relatively easy for the JIT to detect the `frozendict` constructor, the `dict` input, and the single reference immediately overwritten. Not sure if this would ever be worth it.

Great! Now make `set` have a stable order and we're done here.