Python's approach is one of the most confusing ways to possibly do it. Not having proper, discoverable methods is super annoying, and I need to look it up every time anew I use Python because it's so unintuitive.
Of course you can write a generic version of `mkString` (as this method is called in Scala), so it's also just one method no matter the container count.
The Python weirdness is actually a direct result from the language lacking generics…
From typing perspective there is no sense to have Container[T].join() -> str for any T.