text: # View more 3_python 2_tensorflow_old on my Youtube and Youku channel!!!
  
  # Youtube video tutorial: https://www.youtube.com/channel/UCdyjiB5H8Pu7aDTNVXTTpcg
  # Youku video tutorial: http://i.youku.com/pythontutorial
  
  # 1 - why
  
  """
  1. matplotlib is a powerful 3_python data visualization tool;
  2. similar with MATLAB. If know matlab, easy to move over to 3_python;
  3. easy to plot 2D, 3D data;
  4. you can even make animation.
  """