[issue6333] logging: ValueError: I/O operation on closed file

[Sridhar Ratnakumar]

Sridhar Ratnakumar <sridharr at activestate.com> added the comment:

On Thu, 09 Jul 2009 16:43:49 -0700, Vinay Sajip <report at bugs.python.org>
wrote:

> Vinay Sajip <vinay_sajip at yahoo.co.uk> added the comment:
>
>> However, sys.stdout|err can be assigned to some thing else
>> (eg: py.test assigning it to an open file object) .. in which case it
>> is legitimate to handle (close) such objects (handles) by who
>> created it (py.test).
> @Sridhar: I disagree. Creation is not ownership. Clearly ownership is
> *initially* with the creator, but when a stream is used to initialise a
> StreamHandler, ownership of the stream passes to the StreamHandler.

Are you suggesting that the ownership of `sys.stderr` belongs to the
logging module once logging.basicConfig (that initializes a StreamHandler
with stderr) is called? That no other module/library is to close
sys.stderr even though they created it (sys.__stderr__ being the backup)?

StreamHandler can take ownership of an arbitrary stream (say, created by
the caller) passed to it, but assuming ownership of a standard stream,
that are free to be overridden by a library (such as py.test), is rather
bizarre.

> I pointed out in msg90148
> that file-like objects are not guaranteed to have a "closed" attribute,
> to which he has not responded.

If this bug is acknowledged as a problem, then coming up with a fix is a  
different issue. I don't know how to detect whether a stream is closed or  
not .. especially when you say that not all file-like objects have a  
'closed' attribute (BTW, which doesn't?), but this is the only solution I  
know currently:

     ...
     # some streams, such as sys.stdout|err, cannot be owned by  
StreamHandler
     # they might have been closed by whoever customized it.
     closed = hasattr(self.stream, 'closed') and self.stream.closed
     if self.stream and hasattr(self.stream, 'flush') and not closed:
         self.stream.flush()
     ...

-srid

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<http://bugs.python.org/issue6333>
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