I use pylab (more specifically numpy) in all of my python programs. The exceptions are very rare, if any. So far, I have taken the habit of importing numpy in the following
Let's tackle from the other way around, I get your code to debug, and I see that you call:
zeros(5)
it is tedious to go check around your source to see if this is np.zeros or you redefined it somewhere else, and since pylab has 930 names, this can happen easily.