title: python matplotlib.plot does not show chart
body: <p>Have recently started playing with Python. I have installed Python Spyder app on the Mac. Everything has been working well until recently for some reason the matplotlib charts stopped displaying. A simple code like this does  not work anymore:</p>
  
  <pre><code>import matplotlib.pyplot as plt
  x = np.linspace(0.4 * np.pi, 100)
  plt.plot(x)
  </code></pre>
  
  <p>The only output is 
      []</p>
  
  <p>I have Spyder 2.3.3, Python 3.4.3 64 Bit. </p>