- First example is a bit unfair to vanilla python. A better implementation would be the following, which is two times faster (than the given vanilla example):

- First example is a bit unfair to vanilla python. A better implementation would be the following, which is two times faster (than the given vanilla example): from itertools import izip X = xrange(10000000) Y = xrange(10000000) Z = [x + y for x,y in izip(X,Y)] - You didn't mention the difference between flatten() and ravel(). flatten() always makes an explicit copy, ravel() doesn't. - "Arrays must have the same shape to be concatenated with concatenate()." Except for the concatenation axis obviously.