Logging

[Samuel Kilchenmann]

"Neil Benn" <benn at cenix-bioscience.com> schrieb im Newsbeitrag 
news:mailman.1750.1107345636.22381.python-list at python.org...
> Neil Benn wrote:
>
>> Hello,
>>
>>          I'm running a test and having issues with logging, if I call 
>> logging.shutdown() and then want to start the logging going again 
>> then I get a problem as if I call shutdown, I can't get the root 
>> logger again, such as :
>>
>> .<snip>
>
> Previous code missed out a line :
>
> .>>> import logging
> .>>> objTestLogger = logging.getLogger()
> .>>> objTestLogger.setLevel(logging.INFO)
> .>>> objTestLogger.addHandler(logging.FileHandler('c:\\test.log'))
> .>>> objTestLogger.info("THIS IS A TEST")
> .>>> logging.shutdown()
> .>>> objTestLogger = logging.getLogger()
> .>>> objTestLogger.setLevel(logging.INFO)
> .>>> objTestLogger.addHandler(logging.FileHandler('c:\\test.log'))
> .>>> objTestLogger.info("THIS IS A TEST")
> .Traceback (most recent call last):
> . File "c:\program files\python23\lib\logging\__init__.py", line 679, 
> in emit
> .    self.stream.write("%s\n" % msg)
> .ValueError: I/O operation on closed file
> .>>>
>
logging.shutdown() doesn't clean up the dict of handlers at the module 
level and the list of handlers maintained and at the level of the 
manager of loggers. So after calling logging.getLogger() etc. for the 
second time, you still have the closed filehandle in the list of 
loghandlers. The new FileHandler with the open filehandle is appended to 
this list of handlers. Then when you call ...info("...") this call is 
dispatched to all handlers in the handlerlist, i.e. also to the one with 
the closed filehandle.
I don't know if this has to be considered a bug in the logging module or 
if your use case is simply not covered.
If you add something like
.>>> logging._handlers.clear()
.>>> logging.root.handlers = []
.>>> for l in logging.Logger.manager.loggerDict.values():
.>>>     l.handlers = []
after logging.shutdown() and before getting the new logger, your script 
will probably run without errors.

hth,
Samuel