Access URL's from behind a proxy in Python

proxy.py

""" proxy.py

Wires up a proxy server so you can access URL's via Python.

Based on this answer from Stack Overflow: http://stackoverflow.com/a/35443

TODO:
  1. use proper command line args via optparse / OptionParser
"""
import urllib2

def build_opener(proxy):
  """ Returns an OpenerDirector wired up to use the proxy settings passed in the dictionary proxy

  proxy should contain keys / values for:
    - scheme - http
    - url - the proxy server's URL
    - username - the username for the proxy
    - password - the password for the proxy

  """
  passwd_mgr = urllib2.HTTPPasswordMgrWithDefaultRealm()
  passwd_mgr.add_password(None, proxy["url"], proxy["username"], proxy["password"])
  proxy_handler = urllib2.ProxyHandler({proxy["scheme"]: proxy["url"]})
  proxy_auth_handler = urllib2.ProxyBasicAuthHandler(passwd_mgr)

  return urllib2.build_opener(proxy_handler, proxy_auth_handler)

if __name__ == "__main__":
  import sys
  if len(sys.argv) > 4:
    proxy = {}
    proxy["scheme"], proxy["url"], proxy["username"], proxy["password"] = sys.argv[1], sys.argv[2], sys.argv[3], sys.argv[4]
    print proxy
  else:
    print "Usage: ", sys.argv[0], "scheme proxy username password"