>>> a = {'a': 1, 'b': 2}
>>> a.pop('a')
1
>>> a
{'b': 2}
>>> a.pop('a')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
KeyError: 'a'
>>> a.pop('a', 0)
0

import logging
extra = {'app_name':'Super App'}

logger = logging.getLogger(__name__)
syslog = logging.StreamHandler()
formatter = logging.Formatter('%(asctime)s %(app_name)s : %(message)s')
syslog.setFormatter(formatter)
logger.setLevel(logging.INFO)
logger.addHandler(syslog)

logger = logging.LoggerAdapter(logger, extra)
logger.info('The sky is so blue')

logs (something like): 2013-07-09 17:39:33,596 Super App : The sky is so blue