new_contents: #!/usr/bin/env python3
  # -*- coding: utf-8 -*-
  
  # Copyright (c) 2018 Jérémie DECOCK (http://www.jdhp.org)
  
  # Permission is hereby granted, free of charge, to any person obtaining a copy
  # of this software and associated documentation files (the "Software"), to deal
  # in the Software without restriction, including without limitation the rights
  # to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  # copies of the Software, and to permit persons to whom the Software is
  # furnished to do so, subject to the following conditions:
  
  # The above copyright notice and this permission notice shall be included in
  # all copies or substantial portions of the Software.
   
  # THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  # IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  # FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  # AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  # LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  # OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  # THE SOFTWARE.
  
  import sys
  import PyQt5.QtWidgets as widgets
  
  class MainWindow(widgets.QMainWindow):
  
      def __init__(self, *args, **kwargs):
          super().__init__()
  
          label = widgets.QLabel("Hello!")
          self.setCentralWidget(label)
  
          self.show()
  
  if __name__ == '__main__':
      app = widgets.QApplication(sys.argv)
      app.setApplicationName("PyQT Snippets")
  
      window = MainWindow()
  
      exit_code = app.exec_()
      sys.exit(exit_code)
  
subject: Add a widget.