title: Jupyter (IPython) notebook: plot in the qt mode + prompt raw_input()
body: <p>I am trying to plot in Jupyter notebook (Python 2.7), then prompt user for input, save it and then change the plot (this is a crucial point: I don't want to create a new plot, I need to modify the old one after user input). This completely fails to work. Instead of showing the figure and then prompting for input, it opens the figure window, but freezes (doesn't display anything) until I respond to the raw_input() prompt. Only then it plots.</p>
  
  <p>Simple version of the code to show the error:</p>
  
  <pre><code>import matplotlib.pyplot as plt
  %matplotlib qt
  
  fig = plt.figure()
  ax = fig.add_subplot(111)
  ax.plot([1,2,3],[1,2,3])
  plt.show(block=False)
  my_input = raw_input()
  </code></pre>
  
  <p>This bug only appears when I use %matplotlib qt, but I have to use it, because with %matplotlib inline I am unable to modify the plot after it was displayed (at least as far as I am aware). </p>
  
  <p>In fact, I noticed that it freezes until the end of the cell execution, even if it is just time.sleep().</p>
  
  <p>Am I missing something? Some settings of how matplotlib displays figures?</p>