There are a lot of questions about matplotlib, pylab, pyplot, ipython, so I'm sorry if you're sick of seeing this asked. I'll try to be as specific as I can, because I've been looking through people's questions and looking at documentation for pyplot and pylab, and I still am not sure what I'm doing wrong. On with the code:

Goal: plot a figure every .5 seconds, and update the figure as soon as the plot command is called.

My attempt at coding this follows (running on ipython -pylab):

import time
ion()
x=linspace(-1,1,51)
plot(sin(x))
for i in range(10):
    plot([sin(i+j) for j in x])
    #see **
    print i
    time.sleep(1)
print 'Done'

It correctly plots each line, but not until it has exited the for loop. I have tried forcing a redraw by putting draw() where ** is, but that doesn't seem to work either. Ideally, I'd like to have it simply add each line, instead of doing a full redraw. If redrawing is required however, that's fine.

Additional attempts at solving:
just after ion(), tried adding hold(True) to no avail.
for kicks tried show() for **
The closest answer I've found to what I'm trying to do was at http://stackoverflow.com/questions/2310851/plotting-lines-without-blocking-execution, but show() isn't doing anything.

I apologize if this is a straightforward request, and I'm looking past something so obvious. For what it's worth, this came up while I was trying to convert matlab code from class to some python for my own use. The original matlab (initializations removed) which I have been trying to convert follows:

for i=1:time
    plot(u)
    hold on
    pause(.01)
    for j=2:n-1
        v(j)=u(j)-2*u(j-1)
    end
    v(1)= pi
    u=v
end

Any help, even if it's just "look up this_method" would be excellent, so I can at least narrow my efforts to figuring out how to use that method. If there's any more information that would be useful, let me know.