Cute oscillating range generation snippet I saw on irc

[league55]

Iterating both up and down from the middle of a range, with only the range max value input:

import itertools
def spiral(n):
    r1 = range(n // 2, n)
    r2 = range(n // 2 - 1, -1, -1)
    for a, b in itertools.zip_longest(r1, r2):
        yield a
        if b is not None:
            yield b
   

And some application:

list(spiral(6))
[3, 2, 4, 1, 5, 0]