title: Which urllib I should choose?
body: <p>as we know, python has two built-in url lib:   </p>
  
  <ul>
  <li><code>urllib</code> </li>
  <li><code>urllib2</code></li>
  </ul>
  
  <p>and a third-party lib:   </p>
  
  <ul>
  <li><code>urllib3</code></li>
  </ul>
  
  <p>if my requirement is only to request a API by GET method, assume it return a JSON string.<br>
  which lib I should use? do they have some duplicated functions?<br>
  if the <code>urllib</code> can implement my require, but after if my requirements get more and more complicated, the <code>urllib</code> can not fit my function, I should import another lib at that time, but I really want to import only one lib, because I think import all of them can make me confused, I think the method between them are totally different.   </p>
  
  <p>so now I am confused which lib I should use, I prefer <code>urllib3</code>, I think it can fit my requirement all time, how do you think? </p>