Why am I getting an AttributeError when trying to print out

Question

I am learning about urllib2 by following this tutorial http://docs.python.org/howto/urllib2.html#urlerror Running the code below yields a different outcome from the tutorial

import urllib2

req = urllib2.Request('http://www.pretend-o-server.org')
try:
    urllib2.urlopen(req)
except urllib2.URLError, e:
    print e.reason

Python interpreter spits this back

Traceback (most recent call last):
  File "urlerror.py", line 8, in <module>
    print e.reason
AttributeError: 'HTTPError' object has no attribute 'reason'

How come this is happening?

UPDATE

When I try to print out the code attribute it works fine

import urllib2

req = urllib2.Request('http://www.pretend-o-server.org')
try:
    urllib2.urlopen(req)
except urllib2.URLError, e:
    print e.code

Machado

Do you get the same error code if instead print e.reason you put print e.code? – Hankhanke

@Nick Ok now I am getting the AttributeError no matter which URL I pass in and no matter how I import and use urllib2 (and its methods). So everything is working predictably. When I do print e.code I get 404. @agf I'm using 2.6.5 and by the way, how did you get [Errno 11004] getaddrinfo failed. I swear I was getting that same message early today, I took a break, came back, ran the same code again and just get the original AttributeError. I'm thinking ghost in the machine but perhaps I am missing something. – Machado

Answer 1

The reason I got the AttributeError was because I was using OpenDNS. Apparently even when you pass in a bogus URL, OpenDNS treats it like it exists. So after switching to Googles DNS server, I am getting the expected result which is:

[Errno -2] Name or service not known

Also I should mention the traceback I got for running this code which is everything excluding try and except

from urllib2 import Request, urlopen, URLError, HTTPError

req = Request('http://www.pretend_server.com')
    urlopen(req)

is this

Traceback (most recent call last):
  File "urlerror.py", line 5, in <module>
    urlopen(req)
  File "/usr/lib/python2.6/urllib2.py", line 126, in urlopen
    return _opener.open(url, data, timeout)
  File "/usr/lib/python2.6/urllib2.py", line 397, in open
    response = meth(req, response)
  File "/usr/lib/python2.6/urllib2.py", line 510, in http_response
    'http', request, response, code, msg, hdrs)
  File "/usr/lib/python2.6/urllib2.py", line 435, in error
    return self._call_chain(*args)
  File "/usr/lib/python2.6/urllib2.py", line 369, in _call_chain
    result = func(*args)
  File "/usr/lib/python2.6/urllib2.py", line 518, in http_error_default
    raise HTTPError(req.get_full_url(), code, msg, hdrs, fp)
urllib2.HTTPError: HTTP Error 404: Not Found

which a kind gentle(wo)man? from IRC #python told me was highly strange and then asked if I was using OpenDNS to which I replied yes. So they suggested I switch it to Google's which I proceeded to do.

Machado

Answer 2

Depending on the error type, the object e may or may not carry that attribute.

In the link you provided there is a more complete example:

Number 2

from urllib2 import Request, urlopen, URLError
req = Request(someurl)
try:
    response = urlopen(req)
except URLError, e:
    if hasattr(e, 'reason'): # <--
        print 'We failed to reach a server.'
        print 'Reason: ', e.reason
    elif hasattr(e, 'code'): # <--
        print 'The server couldn\'t fulfill the request.'
        print 'Error code: ', e.code
else:
    # everything is fine

Hankhanke

right on, I saw this example and just changed the way I imported urllib2 methods and they way I call them (dropped the urllib2 prefix) and the first example works now. See update. – Machado

@s3z: your code snippets are equivalent. It could be a different error. Change the first snippet to print e.code to see if they indeed differ. – Hankhanke

Nick, Ahh. I realize that I was testing a different URL before. Please check my edited update. Sorry for the confusion. – Machado

Testing for attributes on the error object? Really? This must be the worst object oriented design choice ever. Thanks – Veneering

Answer 3

Because there is no such attribute. Try:

print str(e)

and you will get nice:

HTTP Error 404: Not Found

Lvov

Right but how come it works for the author in the tutorial? How come he gets (4, 'getaddrinfo failed')? – Machado

I tried it, and I get [Errno 11004] getaddrinfo failed so this is definitely not a complete answer. – Gasometer

What OS and python version do you have? – Deflower

Michał, I am using Python 2.6.5 – Machado