Replace default handler of Python logger

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?

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

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