import time

def myflat(lst):
  f = []
  for l in lst: f.extend(l)
  return f

def sumflat(lst):
  return sum(lst, [])

def longlst(n):
  return [[0] for i in xrange(n)]

def timeit(func, *args):
  t1 = time.time()
  func(*args)
  t2 = time.time()
  return t2 - t1

def testtime(func):
  ntry = [10**i for i in range(3, 6)]
  for e in range(3, 6):
    n = 10**e
    t = timeit(func, longlst(n))
    print "10^%d : %f s" % (e, t)

print "myflat():"
testtime(myflat)
print

print "sumflat():"
testtime(sumflat)