various extend metods

>>> import time
>>> def test():
...     """Comapring concat. + vs list.extend vs +="""
...     x = range(10000000)
...     y = range(10000000)
...     x0 = time.clock()
...     z = x + y
...     t1 = time.clock() - x0
...     x1 = time.clock()
...     x.extend(y)
...     t2 = time.clock() - x1
...     x = range(10000000)
...     y = range(10000000)
...     x2 = time.clock()
...     x += y
...     t3 = time.clock() - x2
...     print "+ takes %s, extend takes %s, += takes %s" % (t1, t2, t3)
...     
... 
>>> test()
+ takes 0.13, extend takes 0.06, += takes 0.06
>>>