#!/usr/local/bin/python2
from itertools import chain
chain_from_iterable = chain.from_iterable
l = [[1,2,3,4,5], [6,7,8,9,0], [1,2,3,4,5], [6,7,8,9,0], [1,2,4,5]]
for k in xrange(200000):
  list(chain_from_iterable([i for i in l]))