How can INFO and DEBUG logging message be sent to stdout and higher level message to stderr

Question

Is there an easy way with python's logging module to send messages with a DEBUG or INFO level and the one with a higher level to different streams?

Is it a good idea anyway?

Answer 1

import logging import sys  class LessThanFilter(logging.Filter):     def __init__(self, exclusive_maximum, name=""):         super(LessThanFilter, self).__init__(name)         self.max_level = exclusive_maximum      def filter(self, record):         #non-zero return means we log this message         return 1 if record.levelno < self.max_level else 0  #Get the root logger logger = logging.getLogger() #Have to set the root logger level, it defaults to logging.WARNING logger.setLevel(logging.NOTSET)  logging_handler_out = logging.StreamHandler(sys.stdout) logging_handler_out.setLevel(logging.DEBUG) logging_handler_out.addFilter(LessThanFilter(logging.WARNING)) logger.addHandler(logging_handler_out)  logging_handler_err = logging.StreamHandler(sys.stderr) logging_handler_err.setLevel(logging.WARNING) logger.addHandler(logging_handler_err)  #demonstrate the logging levels logger.debug('DEBUG') logger.info('INFO') logger.warning('WARNING') logger.error('ERROR') logger.critical('CRITICAL') 

Implementation aside, I do think it is a good idea to use the logging facilities in python to output to the terminal, in particular because you can add another handler to additionally log to a file. If you set stdout to be INFO instead of DEBUG, you can even include additional DEBUG information that the user wouldn't standardly see in the log file.