urllib and urllib2

You might be intrigued by the existence of two separate URL modules in Python - urllib and urllib2. Even more intriguing: they are not alternatives for each other. So what is the difference between urllib and urllib2, and do we need them both? 

urllib and urllib2 are both Python modules that do URL request related stuff but offer different functionalities. Their two most significant differences are listed below: 

• urllib2 can accept a Request object to set the headers for a URL request, urllib accepts only a URL. That means, you cannot masquerade your User Agent string etc.
• urllib provides the urlencode method which is used for the generation of GET query strings, urllib2 doesn't have such a function. This is one of the reasons why urllib is often used along with urllib2.
• urllib does not support proxy, but urllib2 can support
  
  

For other differences between urllib and urllib2 refer to their documentations, the links are given in the References section. 

Tip: if you are planning to do HTTP stuff only, check out httplib2, it is much better than httplib or urllib or urllib2.