title: python urllib.open(url) but return history data
body: <p>I use python's urllib library for checking the update of one webpage every 5 sec.
  But after I run the program a few hours, It seems that the urllib.open(url) just returns the outdated data.It usually delays by 5-10mins.I need your help.</p>
  
  <pre><code>    urlItem = urllib.urlopen("http://ka.game.163.com/")
      htmlSource = urlItem.read()
      urlItem.close()
  </code></pre>