2d animation

I've recently started using pylab, and its not clear to me how to do a 2d animation.

If I have a 3d numeric array (eg arr=RandomArray.randint(0,127,(100,256,256)))
how can I display arr[0], then arr[1], then...

The way I've tried seems to slow down as I progress, suggesting that its drawing all previous arrays before drawing the current one.