Recently at work I got the chance to use a couple of #Python features I'd never used before: positional-only arguments, and keyword-only arguments.

If you've never seen this before, the general form is:

def my_function(a, b, /, c, d, *, e, f)

Where a and b *must* be passed as positional (not keyword) arguments, e and f must be passed as keyword (not positional), and c and d can be passed either way.

Still not sure how I feel about them being first-class language features, but they did solve a kind of weird niche problem I was having and that would have needed more code to solve in other ways.