How to check for an HTTP status code of 401?

Question

In one of the answers that I have received here, I encountered a problem of not knowing how to pass automatically through \"Google App Engines\" my ID and a password to a we

Answer 1

In ordinary Python code, I'd probably use the lower-level httplib, e.g.:

import httplib

domains = 'google.com gmail.com appspot.com'.split()

for domain in domains:
  conn = httplib.HTTPConnection(domain)
  conn.request('GET', '/')
  resp = conn.getresponse()
  print 'Code %r from %r' % (resp.status, domain)

this will show you such codes as 301 (moved permanently) and 302 (moved temporarily); higher level libraries such as urllib2 would handle such things "behind the scenes" for you, which is handy but makes it harder for you to take control with simplicity (you'd have to install your own "url opener" objects, etc).

In App Engine, you're probably better off using urlfetch, which returns a response object with a status_code attribute. If that attribute is 401, it means that you need to repeat the fetch with the appropriate kind of authorization information in the headers.

However, App Engine now also supports urllib2, so if you're comfortable with using this higher level of abstraction you could delegate the work to it. See here for a tutorial on how to delegate basic authentication to urllib2, and here for a more general tutorial on how basic authentication works (I believe that understanding what's going on at the lower layer of abstraction helps you even if you're using the higher layer!-).