[ python-Bugs-971965 ] urllib2 raises exception with non-200 success codes.

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Bugs item #971965, was opened at 2004-06-13 05:00
Message generated for change (Comment added) made by jjlee
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Category: Python Library
Group: Python 2.3
Status: Open
Resolution: None
Priority: 5
Private: No
Submitted By: Ed Watkeys (edw)
Assigned to: Nobody/Anonymous (nobody)
Summary: urllib2 raises exception with non-200 success codes.

Initial Comment:
If a server returns a code other than 200, specifically 201 
(Created), urllib2.urlopen will raise an HTTPError exception. I ran 
into this while implementing an Atom API client, which solicits 201 
responses from the server when submitting a blog post.

  File "/usr/local/lib/python2.3/urllib2.py", line 129, in urlopen
    return _opener.open(url, data)
  File "/usr/local/lib/python2.3/urllib2.py", line 326, in open
    '_open', req)
  File "/usr/local/lib/python2.3/urllib2.py", line 306, in _call_chain
    result = func(*args)
  File "/usr/local/lib/python2.3/urllib2.py", line 901, in http_open
    return self.do_open(httplib.HTTP, req)
  File "/usr/local/lib/python2.3/urllib2.py", line 895, in do_open
    return self.parent.error('http', req, fp, code, msg, hdrs)
  File "/usr/local/lib/python2.3/urllib2.py", line 352, in error
    return self._call_chain(*args)
  File "/usr/local/lib/python2.3/urllib2.py", line 306, in _call_chain
    result = func(*args)
  File "/usr/local/lib/python2.3/urllib2.py", line 412, in 
http_error_default
    raise HTTPError(req.get_full_url(), code, msg, hdrs, fp)
urllib2.HTTPError: HTTP Error 201: Created


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Comment By: John J Lee (jjlee)
Date: 2007-07-12 01:15

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Duplicate of 912845, please close.

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Comment By: John J Lee (jjlee)
Date: 2007-03-12 00:11

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Whether 206 and 201 are HTTP success responses is not the question at
hand.  Given that the 206 behaviour was changed, I agree that other success
responses should also be considered (certainly seems a mistake that e.g.
203 was not added at the same time as 206), and indeed nobody has done
that.  But I think backwards compatibility, the semantics of the various
response codes and of urllib2, and ease of understanding, are more
important than you seem to assume.

I don't see a patch.  In what way exactly do you propose urllib2 should be
changed?  Note that it's not completely obvious: e.g. a 201 received by a
plain-urllib2 client would be an erroneous server response, because urllib2
is designed only for retrieving URLs, and is not intended to be a generic
HTTP client.  Also note that clients based on urllib2 that do support PUT,
such as the Atom client you refer to, can easily implement the modified 201
handling themselves.  So on the face of it, the particular issue you raise
is a bug in that code, and not in urllib2.

Of course, your derogatory remarks about authors / bug-fixers won't
persuade anybody of anything, or get any work done.


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Comment By: John Belmonte (jbelmonte)
Date: 2007-03-11 21:23

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Fixing this issue is not "maybe OK", it's the correct thing to do.  
Having an HTTP success response raise an exception is faulty behavior, and
urllib2 users should not have to do silly things to work around it.  It
really seems like the authors of urllib2 only understood about 10% of the
HTTP protocol.

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Comment By: John J Lee (jjlee)
Date: 2005-05-19 21:05

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Before bug 912845 (CVS rev 1.69) added 206 to the list of
response codes considered "successful" by urllib2, I'd
assumed this would never be altered, for
backwards-compatibility reasons.

Note that this behaviour can be configured by module users,
since HTTPError exceptions support the urllib2 response
interface.  This can be done by replacing
HTTPErrorProcessor, or by replacing HTTPDefaultErrorHandler,
or catching the exception "manually".

But maybe since the 206 issue was considered a valid bug
fix, this is OK too.

If so, it would be best if the other 20x responses were also
considered at the same time. 


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