new_contents: #!/usr/bin/env python
  """
  useage example: ./fetch_useful.py https://developer.nvidia.com/deep-learning-courses
  """
  from sys import argv
  import re
  import urllib
  
  ### This needs to make sure again and again!
  url="http://vision.stanford.edu/teaching/cs231b_spring1415/"
  #src_url="http://vision.stanford.edu/teaching/cs231b_spring1415/syllabus.html"
  
  print "NOTE: add url webpage and make sure the fetch url is correct, especially the base url!"
  
  src_url = argv[1]
  print "source webpage: " + src_url
  
  ## first fetch the source HTML page
  urllib.urlretrieve(src_url, filename="syllabus.html")
  
  txt = open("syllabus.html", "r")
  for line in txt:
          index = line.find(".pdf")
  	index_ppt = line.find(".ppt")
          index_mp4 = line.find(".mp4")
          if index != -1 or index_ppt != -1 or index_mp4:
                  lists = line.split("\"")
                  rets = [list for list in lists if list.find(".pdf") != -1 or list.find(".ppt") != -1 or list.find(".mp4") != -1]
                  for ret in rets:
  			# for relative path, combine it with previous path
                          if line.find("http:") == -1:
                                  fetch_url = url + str(ret)
                                  name = str(ret).split("/")[-1]
  				if fetch_url.find("<") == -1 or fetch_url.find(">") == -1:
  					print fetch_url + " ---> " + name
  					urllib.urlretrieve(fetch_url, filename=name)
  			# for absolute path, just use it
                          else:
                                  name = str(ret).split("/")[-1]
  				# fix bugs: ret may not contain "http", just with "ppt/pdf"(line has but ret not)
  				if ret.find("http:") != -1:
  					print ret + " ---> " + name
                                  	urllib.urlretrieve(ret, filename=name)
  
subject: add script for fetching nvidia course