new_contents: # main.py
  
  # Imports
  import sys
  from PyQt4 import QtGui
  from mainwindow import MainWindow
  
  # main
  def main():
      qapp = QtGui.QApplication(sys.argv)
      
      mainwindow = MainWindow()
      mainwindow.show()
  
      qapp.exec_()
  
  if __name__ == '__main__':
      main()    
  
  
subject: Add main.py