old_contents: from PyQt5.QtWidgets import QApplication
  
  from core.gui import GUI
  from core.config import Config
  
  if __name__ == '__main__':
      import sys
  
      app = QApplication(sys.argv)
  
      config = Config()
      screen = GUI(config)
      
      sys.exit(app.exec_())
new_contents: #! /usr/bin/env python3
  from PyQt5.QtWidgets import QApplication
  
  from core.gui import GUI
  from core.config import Config
  
  if __name__ == '__main__':
      import sys
  
      app = QApplication(sys.argv)
  
      config = Config()
      screen = GUI(config)
      
      sys.exit(app.exec_())
subject: make it executable