title: Matplotlib animation either freezes after a few frames or just doesn't work
body: <p>I've been trying for hours to get this simple script working, but nothing I do seems to help. It's a slight modification of the most basic animated plot sample code from the Matplotlib website, that should just show a few frames of noise (I have the same issue with the unmodified code from their website BTW).</p>
  
  <p>On my computer with the TkAgg backend I get about 20 frames (out of 60) before the plot window freezes. With Qt4Agg I just get a frozen, black window and no frames at all are plotted. I've tried multiple combinations of different NumPy, PyQt, Python and Matplotlib versions, but always get the same result.</p>
  
  <p>Please let me know if this works for you or if anything looks wrong. I'm pretty sure this did work in the past, so I'm thinking it may be a Windows issue or something related to <code>ion()</code>.</p>
  
  <p>FYI I'm using Windows 7 (32 bit) and I've tested with Python 2.6/2.7, MPL 1.0.0/0.9.9.8, PyQt 4.6/4.7, Numpy 1.4/1.5b.</p>
  
  <pre><code>import matplotlib
  matplotlib.use('TkAgg') # Qt4Agg gives an empty, black window
  from pylab import *
  import time
  
  ion()
  hold(False)
  
  # create initial plot
  z = zeros(10)
  line, = plot(z)
  ylim(-3, 3)
  
  for i in range(60):
      print 'frame:', i
  
      d = randn(10)
      line.set_ydata(d)
  
      draw()
      time.sleep(10e-3)
  </code></pre>
  
  <p>This simpler version also freezes after the first couple frames:</p>
  
  <pre><code>from pylab import *
  
  ion()
  hold(False)
  
  for i in range(40):
      plot(randn(10))
      draw()
  
  show()
  </code></pre>
  
  <p>Thanks!</p>
  
  <p><strong>EDIT</strong>: These people seem to be having the same or a similar problem as me:</p>
  
  <ul>
  <li>mail-archive.com/matplotlib-users@lists.sourceforge.net/msg10844.html</li>
  <li>stackoverflow.com/questions/2604119/matplotlib-pyplot-pylab-not-updating-figure-while-isinteractive-using-ipython</li>
  <li>mail-archive.com/matplotlib-users@lists.sourceforge.net/msg01283.html</li>
  </ul>
  
  <p>Doesn't look like any of them were able to fix it either :(</p>