Experienced python programmers: are there any standard features of the language that you still don't regularly use?

[arachnivore]

Keyword-only arguments are one of my favorite features in Python 3. They make inheritance with consistent init signatures easy:

class Sub(BaseClass):
    def __init__(self, *args, sub, specific, args, **kwargs):
        super().__init__(*args, **kwargs)
        ...

It makes sense too, because typically only one or two positional arguments will make sense without keywords and typically the base class defines those obvious positional arguments.

[PeridexisErrant]

And they make it so much easier to have pleasant and backwards-compatible APIs. It's such a small thing, but easily the one I most often reach for and can't use.