[masklinn]

> I disagree with only one thing in this article. Frozenset is super useful.

Many of the "don't" callables are useful and I'd say I've used about half (`format` is especially nice as a more flexible version of `str`).

But Python's tendency to mutability and the `set` interface makes frozenset verbose to use & have higher overhead than sets[0]. Usually code is terser and just as clear using sets without mutating them. Which is a shame as of course you lose the safety of enforcing immutability (at runtime but still).

Then again, I guess if you're using a type checker it matters less: it shouldn't let you mutate a `set` if you've typed it as `Set` (rather than `MutableSet`).

[0] IIRC there's only one operation which is specifically optimised for frozensets: copy