title: how to use two level proxy setting in Python?
body: <p>I am working on web-crawler [using python].</p>
  
  <p>Situation is, for example, I am behind server-1 and I use proxy setting to connect to the Outside world. So in Python, using proxy-handler I can fetch the urls.
  Now thing is, I am building a crawler so I cannot use only one IP [otherwise I will be blocked]. To solve this, I have bunch of Proxies, I want to shuffle through. </p>
  
  <p>My question is: This is two level proxy, one to connect to main server-1, I use proxy and then after to shuffle through proxies, I want to use proxy. How can I achieve this?</p>