Logging question

[Jean-Michel Pichavant]

Gabor Urban wrote:
> Hi guys,
>
> I have embarassing problem using the logging module. I would like to
> encapsulate the creation and setting up  of the logger in a class, but
> it does not seem working.
>
> Here are my relevant parts of the code:
>
> --
> import sys
> import logging
>
> class LogClass:
>     def __init__(self, fileName, loggerName = 'classLog'):
>         self.Logger = logging.getLogger(loggerName)
>         self.traceName = fileName
>         handler = logging.FileHandler(self.traceName,'a')
>         formatter = logging.Formatter("%(name)s %(asctime)s
> %(filename)s %(lineno)d %(levelname)s %(message)s")
>         handler.setFormatter(formatter)
>         self.Logger.addHandler(handler)
>         self.Handler = handler
>
>     def closeLog(self):
>         self.Handler.flush()
>         self.Handler.close()
>
>     def fetchLogger(self):
>         return self.Logger
>
> if __name__ == "__main__":
>     name = 'testlog.trc'
>     classLog = LogClass(name)
>     logger = classLog.fetchLogger()
>     logger.info("Created")
>     logger.debug("Test")
>     logger.info("Created .. ")
>     logger.debug("Test data")
>     classLog.closeLog()
>
> --
>
> The trace file is created properly but contains no lines at all. If I
> put the code directly in __main__, it works fine.
>
> What did I miss? Any ideas are wellcome.
>
> Gabor
>   
As pointed out you should definitely split the logger creation from its 
configuration, here are my 2 cents:

import logging

_LOGGER_NAME = 'foo'

class MyFileHandler(logging.FileHandler):
    FORMAT = '%(name)s %(asctime)s %(filename)s %(lineno)d %(levelname)s 
%(message)s'

    def __init__(self, fileName):
	logging.FileHandler.__init__(self, fileName, 'a')
        self.setFormatter(logging.Formatter(self.FORMAT))

if __name__ == '__main__':
	# split creation from configuration
	# creation
	logger = logging.getLogger(_LOGGER_NAME)
	# configuration
	logger.addHandler(MyFileHandler('anyfile.tmp'))
	logger.setLevel(logging.DEBUG)
	logger.info('bar')

I personally use the following pattern:

In any submodule moduleA.py of an application:

import MyApp
_logger = logging.getLogger(MyApp.logger.name + '.moduleA') # attach my 
logger to MyApp logger
# Configuration : nothing to be done, relies on MyApp configuration logger

# You can add code in case you are executing your module in standalone 
mode (for unit testing for instance)

if __name__ == '__main__':
	_logger = logging.getLogger('moduleA')
	_logger.addHandler(logging.FileHandler('moduleA.test','a'))
	# here is some unit tests



Jean-Michel