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errno and strerror attributes incorrectly set on socket errors wrapped by urllib #50720Description
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assignee = None
closed_at = None
created_at = <Date 2009-07-12.20:54:33.896>
labels = ['type-bug', 'library', '3.9', '3.10', '3.11']
title = 'errno and strerror attributes incorrectly set on socket errors wrapped by urllib'
updated_at = <Date 2021-11-30.20:20:38.331>
user = 'https://github.com/ezio-melotti' bugs.python.org fields:
activity = <Date 2021-11-30.20:20:38.331>
actor = 'iritkatriel'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2009-07-12.20:54:33.896>
creator = 'ezio.melotti'
dependencies = []
files = ['26559']
hgrepos = []
issue_num = 6471
keywords = ['patch']
message_count = 9.0
messages = ['90458', '90462', '90466', '100178', '166705', '167330', '170710', '170723', '407399']
nosy_count = 9.0
nosy_names = ['georg.brandl', 'amaury.forgeotdarc', 'orsenthil', 'ezio.melotti', 'r.david.murray', 'chris.jerdonek', 'catherine', 'denkoren', 'iritkatriel']
pr_nums = []
priority = 'normal'
resolution = None
stage = 'needs patch'
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue6471'
versions = ['Python 3.9', 'Python 3.10', 'Python 3.11'] Linked PRs
Activityezio-melotti commented on Jul 12, 2009 In Python 2.6, socket.error was changed to be a child class of IOError
1. IOError derives from EnvironmentError 2, and EnvironmentError
accepts a 2-tuple used to set the values of the errno and strerror
attributes respectively 3.
Apparently the IOError raised by the socket module are instantiated
passing (always?) 'socket error' as first arg and an instance of
socket.gaierror, socket.timeout or socket.herror (and maybe others) as
second arg.
The errno attributes ends up being a string (and not a number) and the
strerror another exception (and not a str):
>>> import socket
>>> from urllib import urlopen
>>> socket.setdefaulttimeout(0.01)
>>> try: urlopen('http://www.python.org')
... except Exception, e: err1 = e
...
>>> err1
IOError('socket error', timeout('timed out',))
>>> err1.errno
'socket error'
>>> err1.strerror
timeout('timed out',)
>>> err1.strerror.errno
>>> err1.strerror.strerror
>>>
>>> try: urlopen('http://www.pythonfoobarbaz.org')
... except Exception, e: err2 = e
...
>>> err2
IOError('socket error', gaierror(11001, 'getaddrinfo failed'))
>>> err1.errno
'socket error'
>>> err1.strerror
timeout('timed out',)
>>> err1.strerror.errno
>>> err2.errno
'socket error'
>>> err2.strerror
gaierror(11001, 'getaddrinfo failed')
>>> err2.strerror.errno
11001
>>> err2.strerror.strerror
'getaddrinfo failed'The 'socket error' strings doesn't provide any useful information
(herror, gaierror and timeout are already subclasses of socket.error)
and it results in confusing messages like:
IOError: [Errno socket error] [Errno 11001] getaddrinfo failed
The relevant information is not accessible directly on the error but it
is in err.strerror/err.args1.
IMHO the first arg should be the errno (if it's available) and the
second the message (e.g. 'getaddrinfo failed' or 'timed out').
The doc of socket.error 1 should be also changed because it says:
"The accompanying value is either a string telling what went wrong or a
pair (errno, string) representing an error returned by a system call,
similar to the value accompanying os.error." (and this is actually what
I'd like it to be, but right now it's something different.) amauryfa commented on Jul 12, 2009 No, it seems that 2.5 has the same problem. The 'socket error' message is
raised in urllib.py. The socket module is innocent to me...
It appears that this file routinely raises IOErrors, passing various
arguments, which are not stored properly in the IOError object. IMO it
should raise subclasses of IOError.
In this particular case of "socket error", it should let the exception
propagate. Other occurrences need more thinking. bitdancer commented on Jul 13, 2009 Yes, it looks to me like urllib is intentionally putting the 'socket
error' or 'url error' into the errno position in the IOError arguments.
Now that socket.error is an IOError, that at least seems wrong. changed the title [-]errno and strerror attributes incorrectly set on socket.error[/-] [+]errno and strerror attributes incorrectly set on socket errors wrapped by urllib[/+] on Jul 13, 2009ezio-melotti commented on Feb 27, 2010 Can this be fixed without breaking compatibility?
It also affects Python2.7 and maybe also Python 3.x (there the error is different and might be intentional).
Copy/pastable snippet to reproduce the error on 2.x:
from urllib import urlopen
try:
urlopen('http://www.pythonfoobarbaz.org')
except Exception, err:
print 'err:', err
print 'repr(err):', repr(err)
print 'err.errno:', err.errno
print 'err.strerror:', err.strerror
print 'err.strerror.errno:', err.strerror.errno
print 'err.strerror.strerror:', err.strerror.strerror
Result on 2.7:
err: [Errno socket error] [Errno -2] Name or service not known
repr(err): IOError('socket error', gaierror(-2, 'Name or service not known'))
err.errno: socket error
err.strerror: [Errno -2] Name or service not known
err.strerror.errno: -2
err.strerror.strerror: Name or service not known
Copy/pastable snippet to reproduce the error on 3.x:
from urllib.request import urlopen
try:
urlopen('http://www.pythonfoobarbaz.org')
except Exception as exc:
err = exc
print('err:', err)
print('repr(err):', repr(err))
print('err.errno:', err.errno)
print('err.strerror:', err.strerror)
print('err.reason:', err.reason)
print('err.reason.errno:', err.reason.errno)
print('err.reason.strerror:', err.reason.strerror)
Result on 3.2:
err: <urlopen error [Errno -2] Name or service not known>
repr(err): URLError(gaierror(-2, 'Name or service not known'),)
err.errno: None
err.strerror: None
err.reason: [Errno -2] Name or service not known
err.reason.errno: -2
err.reason.strerror: Name or service not known catherine commented on Jul 29, 2012 It's very hard to tell what ought to be done here, since Lib/urllib/request.py throws URLErrors with a great variety of order and number of arguments, and it's not clear how URLError (in Lib/urllib/error.py) intends to handle them.
However, in this case, AbstractHTTPHandler.do_open is instantiating URLError with another exception instance, and that exception contains .errno and .strerror. URLError puts the entire error instance into reason, where the information is hidden away as .reason.strno and .reason.strerror.
In the name of keeping this information available rather than hiding it, I'm attaching a patch that adds to URLError.__init__:
if hasattr(reason, "errno"):
self.errno = reason.errno
if hasattr(reason, "strerror"):
self.strerror = reason.strerrorAgain, I'm not sure this is the most logical approach because I can't find a consistent pattern in the ways URLError is instantiated. bitdancer commented on Aug 3, 2012 This is an interesting idea and should at least improve matters. I'm wondering, though...I seem to remember writing code that fished the wrapped error out using one of those attributrs...but I'm not at a computer where I can try to check on that. Hopefully I can check on it this weekend. ezio-melotti commented on Sep 19, 2012
I seem to remember writing code that fished the wrapped error
out using one of those attributrs...
That would be err.reason:
from urllib.request import urlopen
try:
urlopen('http://www.pythonfoobarbaz.org')
except Exception as exc:
print('err:', err)
print('repr(err):', repr(err))
print('err.reason:', err.reason)
print('repr(err.reason):', repr(err.reason))prints:
err: <urlopen error [Errno -2] Name or service not known>
repr(err): URLError(gaierror(-2, 'Name or service not known'),)
err.reason: [Errno -2] Name or service not known
repr(err.reason): gaierror(-2, 'Name or service not known') bitdancer commented on Sep 19, 2012 Ah, of course. I should have reread the whole issue :)
The backward compatibility is the big concern here. Regardless of what we do about that, we should at least fix this in 3.4. vasiliyk commented on Oct 21, 2026 Still reproduces on 3.16.0a1+dev:
>>> from urllib.request import urlopen
>>> try:
... urlopen('http://www.pythonfoobarbaz.org')
... except Exception as exc:
... err = exc
... print('err:', err)
... print('repr(err):', repr(err))
... print('err.errno:', err.errno)
... print('err.strerror:', err.strerror)
... print('err.reason:', err.reason)
... print('err.reason.errno:', err.reason.errno)
... print('err.reason.strerror:', err.reason.strerror)
...
err: <urlopen error [Errno 8] nodename nor servname provided, or not known>
repr(err): URLError(gaierror(8, 'nodename nor servname provided, or not known'))
err.errno: None
err.strerror: None
err.reason: [Errno 8] nodename nor servname provided, or not known
err.reason.errno: 8
err.reason.strerror: nodename nor servname provided, or not knownURLError.__init__ sets only args and reason, so the OSError attributes are never set.
Following the original patch:
- in
URLError.__init__, if reason is an OSError, copy its errno and strerror.
args, str() and repr() do not change, so the backward-compatibility concern does not apply.
I can open a PR with tests if this approach is fine. orsenthil commented on Oct 29, 2026 @vasiliyk, please create the patch with the approach. Reacted by Vasiliy Kiryanov vasiliyk commented on Oct 30, 2026 @orsenthil The PR is up - #160938. I added a a versionchanged note for 3.16 in urllib.error doc. orsenthil commented on Oct 31, 2026 Thanks for this patch. This shouldn't be backported as there is subtle scenario wherein if an old code was checking e.errno is None previously to fall back on OSError, it will break and will need a change.
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