> from pylab import *
--pylab[=option] is almost technically equivalent to
%pylab option as the difference that you cannot un-pylab a
--pylab kernel, but you can restart a
%pylab is a little more that just
from pylab import * (see
%pylab?for a longer explanation), but in short yes it imports a lot of things, but it also hooks event loops (qt, wx, osx...) and set-up some display hooks for matplotlib (the things that magically allow you to get inline graph). Setting the display-hook is closer to something like
sympy.init_printing() if you wonder.
Note that starting at IPython 1.0 we recommend not to use
%pylab (unless you know exactly the implication). We provide
%matplotlib that only init the display hook.
%pylab will warn you if it replaced a few object in current namespace, and which ones. This is useful especially for functions like
sum which do not have the same behavior the behavior with and without pylab and leads to subtle bugs.
We consider now that
--pylab was a mistake, but that it was still really usefull at the beginning of IPython. We all know that
Explicit is better than implicit so if you can advise people not to use
%pylab we would appreciate it, to one day get rid of it.
Extract from %pylab help that give only the import part of pylab:
%pylab makes the following imports:: import numpy import matplotlib from matplotlib import pylab, mlab, pyplot np = numpy plt = pyplot from IPython.display import display from IPython.core.pylabtools import figsize, getfigs from pylab import * from numpy import *