Positional-only parameters for Python

not only that, _ is the conventional name of any variables that you're going to ignore. Which is really handy for a lot of things;

iterating over containers of containers:

for a, b, _ in [(1, 'a', []), (2, 'b', [])]: ...

for functions that need to fulfill an interface:

def f1(f: str, *, opt: bool = False):
def f2(f: str, **_):

myval = [f(myval, opt=True) for f in [f1, f2]]

with the python3 partial container explosion syntax:

a, b, *_ = (1, 2, 3, 4)

and a bunch of other cases.