Solution to http://www.reddit.com/r/dailyprogrammer/comments/q2v2k/2232012_challenge_14_easy/

ch14.py

#!/usr/bin/python2

ex = [1, 2, 3, 4, 5, 6]
bs = 2

def extract(lst, bs):
    result = []
    for i in range(bs):
        result.append(lst.pop())
    result.reverse()
    return result

def populate(lst, bs):
    result = []
    while len(lst) > 0:
        result.extend(extract(lst, bs))
    result.reverse()
    return result

print populate(ex, bs)