what does 'for _ in range()' mean?

[Phil Frost]

At Some Point, Someone Asked Something to The Effect of:
> where does this _ thing come from?

In ML, _ is used as magic "don't care" variable. It's often used when
unpacking tuples and some elements are irrelevant. Example:

Ocaml:
let (fu, bar, _, _) = returns_a_4_tuple ()

Python:
(fu, bar, _, __) = returns_a_4_tuple()

One difference is that _ is allowed multiple times in Ocaml, while in
Python it is not. Also to Python, it's a variable like any other, while
in Ocaml it's magic.