title: PyQt4: Restart main event loop/ Continue GUI for multiple execution of same algorithm
body: <p>I am using PyQt4 to create a GUI that reads, processes and saves the processed image. In algorithmic point of view program is working quite well. But I encountered a small problem in GUI programming.
  In current state, the application need to be launched every time to process every new image. 
  My main() consists of following codes:</p>
  
  <pre><code>      app = QApplication(sys.argv)
        window = mainwindow()
        sys.exit(app.exec_())
  </code></pre>
  
  <p>which I suppose is a fundamental for launching application in PyQt.</p>
  
  <p>I want the user to be able to process different images without closing and opening application for each image. I have a final button "Process" to process and save the image. I was wondering if I could emit some signal that would restart the main event loop after all the processes. I have fair understanding of signal and slot but I am not sure how to restart the main loop.</p>
  
  <p>I have looked previous questions and tried some of their suggestions. But either I was too stupid or they were simply not the solution to my problem. I would appreciate your help.</p>
  
  <p>Thank you in advance. </p>