How do I change the format of a Python log message on a per-logger basis?
After reading the documentation on logging
, I know I can use code like this to perform simple logging:
import logging
def main():
logging.basicConfig(filename="messages.log",
level=logging.WARNING,
format='%(filename)s: '
'%(levelname)s: '
'%(funcName)s(): '
'%(lineno)d:\t'
'%(message)s')
logging.debug("Only for debug purposes\n")
logging.shutdown()
main()
However, I realised I don't know how to change the format of log messages on a per-logger basis, since basicConfig
is a module-level function. This code works for creating different loggers with different levels, names, etc. but is there a way to change the format of those log messages on a per-logger basis as well, in a way similar to basicConfig
?
import inspect
import logging
def function_logger(level=logging.DEBUG):
function_name = inspect.stack()[1][3]
logger = logging.getLogger(function_name)
logger.setLevel(level)
logger.addHandler(logging.FileHandler("{0}.log".format(function_name)))
return logger
def f1():
f1_logger = function_logger()
f1_logger.debug("f1 Debug message")
f1_logger.warning("f1 Warning message")
f1_logger.critical("f1 Critical message")
def f2():
f2_logger = function_logger(logging.WARNING)
f2_logger.debug("f2 Debug message")
f2_logger.warning("f2 Warning message")
f2_logger.critical("f2 Critical message")
def main():
f1()
f2()
logging.shutdown()
main()
Try this
import logging
logger = logging.getLogger('simple_example')
logger.setLevel(logging.DEBUG)
# create file handler that logs debug and higher level messages
fh = logging.FileHandler('spam.log')
fh.setLevel(logging.DEBUG)
# create console handler with a higher log level
ch = logging.StreamHandler()
ch.setLevel(logging.ERROR)
# create formatter and add it to the handlers
formatter = logging.Formatter(
'%(asctime)s - %(name)s - %(levelname)s - %(message)s')
ch.setFormatter(formatter)
fh.setFormatter(formatter)
# add the handlers to logger
logger.addHandler(ch)
logger.addHandler(fh)
# 'application' code
logger.debug('debug message')
logger.info('info message')
logger.warn('warn message')
logger.error('error message')
logger.critical('critical message')
See http://docs.python.org/howto/logging-cookbook.html#multiple-handlers-and-formatters for more information
You have to create or use an existing subclass of logging.Handler
and call the setformatter()
method of an instance thereof with an instance of a custom subclass of logger.Formatter
. If you set the formatter for a handler that was already attached to the logger you want to modify the output of, you are fine, otherwise you have to retrieve a logger object with logging.getLogger()
and call its addHandler()
method with the instance of your handler class that you set the formatter on as the argument.