For inline ipython, you want to switch to the object-oriented use of
pylab. Something like this should work with xlim.
fig = plt.figure()
a = [0.1, 0.2, 0.1]
ax = fig.add_subplot(111)
ax.errorbar(arange(3), a, yerr=a-sum(a)/len(a), fmt='ro')
I'm not aware of automatic settings for padding, but with this
set_xlim, it's easy enough to roll your own using the data limits.