404 errors

[Ivan Karajas]

On Tue, 27 Apr 2004 10:46:47 +0200, Tut wrote:

> Tue, 27 Apr 2004 11:00:57 +0800, Derek Fountain wrote:
> 
>> Some servers respond with a nicely formatted bit of HTML explaining the
>> problem, which is fine for a human, but not for a script. Is there some
>> flag or something definitive on the response which says "this is a 404
>> error"?
> 
> Maybe catch the urllib2.HTTPError?

This kind of answers the question. urllib will let you read whatever it
receives, regardless of the HTTP status; you need to use urllib2 if you
want to find out the status code when a request results in an error (any
HTTP status beginning with a 4 or 5). This can be done like so:
 
import urllib2
try:
    asock = urllib2.urlopen("http://www.foo.com/qwerty.html")
except urllib2.HTTPError, e:
    print e.code

The value in urllib2.HTTPError.code comes from the first line of the web
server's HTTP response, just before the headers begin, e.g. "HTTP/1.1 200
OK", or "HTTP/1.1 404 Not Found".

One thing you need to be aware of is that some web sites don't behave as
you would expect them to; e.g. responding with a redirection rather than a
404 error when you when you request a page that doesn't exist. In these
cases you might still have to rely on some clever scripting.

Cheers,

Ivan