A “frozen” dictionary for Python

I wonder whether Raymond Hettinger has an opinion on this PEP. A long time ago, he wrote: "freezing dicts is a can of worms and not especially useful".

https://mail.python.org/pipermail/python-dev/2006-February/0...

This is why I love how Rust approached this; almost by accident to make borrow checking work. Every reference is either mutable or not, and (with safe code), you can't use an immutable reference to get a mutable reference anywhere down the chain. So you can slowly construct a map through a mutable reference, but then return it out of a function as immutable, and that's the end of it. It's no longer ever mutable, and no key or value is either. There's no need to make a whole new object called FrozenHashMap, and then FrozenList, and FrozenSet, etc. You don't need a StringBuilder because String is mutable, unless you don't want it to be. It's all just part of the language.

Kotlin _kinda_ does this as well, but if you have a reference to an immutable map in Kotlin, you are still free to mutate the values (and even keys!) as much as you like.