run ipython in emacs, matplotlib after plot.show( ), the ipython buffer remains hanging

I was learning how to plot in python using the matplotlib library.
when I started in the terminal with

tommy@tommy-ThinkPad-T420:~$ ipython --pylab

In [1]: plot(range(4))
Out[1]: [<matplotlib.lines.Line2D at 0x37b4b50>]

the figure showed up automatically, and the prompt was active in the shell.

However, when I run it through emacs, the figure did not show up until I typed plot.show( ),
and the ipython buffer is inactive unless you close the figure.  If you type plot.show( ) again,
nothing will show up.

A quick google:

http://stackoverflow.com/questions/9753885/pylab-matplotlib-show-waits-until-window-closes

" Add pylab.ion() (interactive mode) before the pylab.show() call. That will make the UI run in a separate thread and the call to show will return immediately."