BUG URLLIB2

[John Hunter]

>>>>> "bart" == bart  <e_viola at libero.it> writes:

    bart> I'm an italian student and my problem consists about
    bart> urllib2; urlopen function, sometimes, give me old (and
    bart> inexactly) url because the site has moved in a new location
    bart> but urlopen doesn't undestand it and return 403 error
    bart> FORBIDDEN.

I don't think you can describe this as a bug; it's a feature!  python
provides exceptions to handle, well, exceptional circumstances, such
as trying to access a web site that you are forbidden to access.  When
this happens, an 'exception' is raised, and there is a mechanism to
handle the exception.

A simple example

  class MyClass:
      def __init__(self, x):
      self.x = x
  
  c = MyClass(1)
  
  print c.x  # ok
  print c.y  # illegal, an AttributeError is raised       

In order to try something that might raise an exception, enclose it in
try/except blocks

  try: print c.x
  except AttributeError: 'There is no attribute x'
  
  try: print c.y
  except AttributeError: 'There is no attribute y'

There are lots of kinds of kinds of exceptions, and individual modules can
create their own.  Suppose we wanted to divide some number by y, but
y equals 0

  y = 1
  print 2/y  # this is ok
  
  y = 0
  print 2/y  # this is not so good, and will raise a ZeroDivisionError

You can define default behavior if someone tries to divide by zero by
handling the exception

  try: print 2/y
  except ZeroDivisionError: print 'You are about to explode!'

Now, to make a long story short, you need to handle the
urllib2.HTTPError exception in your example

  try: con=urllib2.urlopen('http://www.google.it/search')
  except urllib2.HTTPError: print "Can't read the web site, try again!"

For a tutorial introduction to exceptions, see
http://python.org/doc/current/tut/node10.html

For future reference: python is a mature language and it is a rare
experience indeed to find a bug.  User error is far more common.
Also, cross posting the question to many USENET groups and mailing
lists is generally frowned upon.  If it is a python question and you
post to this group alone, chances are good that you'll get a reply
within the hour, usually much sooner.

Good luck!
John Hunter