Nope, don't need to. WebStorm can even detect nonexistent attributes for objects whose format the back-end decides, and tbh I'm not sure what sort of sorcery it uses.

OP suggested that linters for python won't catch attribute errors, which they 100% will if you use type hints, as you should.

What happens at runtime is really relevant in this case.

Holy crap that's wild, new phones autocorrect is out to get me

How does "foo" mean "get"? Half the battle of writing correct code is writing code that's easy to interpret. Do you always look at the guts of every function you're about to use?

I would do

class MyClass:
    def __init__(self, value):
        self._whatever = value

    @property
    def whatever(self):
        return self._whatever

Personally, I would type hint all of that but I'm just showing how you can do it without types. Your linter should be smart enough to say "hey dumbass did you mean this other thing"? Also since we didn't create a setter you can't arbitrarily overwrite the value of whatever so thats neat.

And I'll just say before I post that I'm on mobile and I'm sorry if the formatting is fucked. I'm not going to fix it.

I use a spell checker in my IDE. It would catch this.

What's the purpose of foo? Why an ambiguous single character variable? What if the property was there but the value was null? Why not use (assuming JS) optional chaining?

I'd approach it more like this:

function getWhatevrProp(userData) (
  const default = { whatevr: "n/a" };

  return { ...default, ...userData }.whatevr;
}

Sorry, read too fast the first time. It's more likely Python. I also don't know Python well enough to give recommendations on that.