use custom parameter in logging formatter

gistfile1.py

import logging

log = logging.getLogger()
log.setLevel(logging.DEBUG)

h = logging.StreamHandler()
f = logging.Formatter('%(message)s,%(my_param)s')
h.setFormatter(f)
log.addHandler(h)

# use "extra" argument
log.debug('foo', extra={'my_param': 100})
log.debug('bar', extra={'my_param': 200})

# foo,100
# bar,200