Replace default handler of Python logger

Question

I've got the following code running on each request of a wsgi (web2py) application:

import logging, logging.handlers from logging import StreamHandler, Formatter  def get_configured_logger(name):      logger = logging.getLogger(name)      if (len(logger.handlers) == 0):         # This logger has no handlers, so we can assume it hasn't yet been configured (Django uses similiar trick)          # === Configure logger ===          # Create Formatted StreamHandler:         FORMAT = "%(process)s %(thread)s: %(message)s"         formatter = logging.Formatter(fmt=FORMAT)         handler = logging.StreamHandler()         handler.setFormatter(formatter)         logger.addHandler(handler)         logger.setLevel(logging.DEBUG)         logger.debug('CONFIGURING LOGGER')      return logger  # Get app specific logger: logger = get_configured_logger(request.application) logger.debug("TEST") 

It's meant to configure the logger once, with the formatted handler I want. It works, except that I'm getting double entries in my stdout:

81893 4329050112: CONFIGURING LOGGER DEBUG:dummy:CONFIGURING LOGGER 81893 4329050112: TEST DEBUG:dummy:TEST 

How do I use my new formatted handler and get rid of/hide the default one?

Answer 1

Perhaps the following example will help. Basically you can either remove the handlers of the logger you'd like to disable, or don't propagate with the logger you are logging from.

$ cat testlog.py import logging logging.basicConfig(filename='foo', level=logging.DEBUG) root_logger = logging.getLogger() root_logger.debug('bar')  my_logger = logging.getLogger('my_logger') FORMAT = "%(process)s %(thread)s: %(message)s" formatter = logging.Formatter(fmt=FORMAT) handler = logging.StreamHandler() handler.setFormatter(formatter)  my_logger.addHandler(handler) my_logger.setLevel(logging.DEBUG) my_logger.info('baz')  my_logger.propagate = False my_logger.info('foobar')  my_logger.propagate = True my_logger.info('foobaz') root_logger.handlers = [] my_logger.info('barbaz')  $ python testlog.py 5927 140735224465760: baz 5927 140735224465760: foobar 5927 140735224465760: foobaz 5927 140735224465760: barbaz  $ cat foo DEBUG:root:bar INFO:my_logger:baz INFO:my_logger:foobaz 

Answer 2

You can remove the default handler from the getLogger() using this:

logging.getLogger().removeHandler(logging.getLogger().handlers[0]) 

Or clear the existing handlers first before adding handlers that you want:

logging.getLogger().handlers.clear() 

After doing so, these logs will no longer display except the new handlers you have added:

DEBUG: Do stuff WARNING: Do stuff