title: PyQt: app.exec_() stops all following code from running
body: <p>I have a code which looks like:</p>
  
  <pre><code>app = QApplication(sys.argv)
  self.interface = Interface()
  
  # The figure
  self.fig = self.interface.fig
  self.ax = self.fig.add_subplot(111)
  
  self.interface.show()
  app.exec_()
  
  print 'this is not printed'
  </code></pre>
  
  <p>The problem is that once <code>app.exec_()</code> is executed, nothing is until I close the window that pops up. </p>
  
  <p>How can I continue running the code?</p>