Python logging across multiple modules with custom handler/filter and splitting loglevels between stdout/stderr

log.py

#!/usr/bin/env python3

import logging
import sys

import sublog

logger = logging.getLogger()

# http://stackoverflow.com/a/24956305/1076493
# filter messages lower than level (exclusive)
class MaxLevelFilter(logging.Filter):
    def __init__(self, level):
        self.level = level

    def filter(self, record):
        return record.levelno < self.level

def main():
    # redirect messages to either stdout or stderr based on loglevel
    # stdout < logging.WARNING <= stderr
    formatter = logging.Formatter('%(asctime)s %(levelname)s [%(module)s]: %(message)s')
    logging_out = logging.StreamHandler(sys.stdout)
    logging_err = logging.StreamHandler(sys.stderr)
    logging_out.setFormatter(formatter)
    logging_err.setFormatter(formatter)
    logging_out.addFilter(MaxLevelFilter(logging.WARNING))
    logging_out.setLevel(logging.DEBUG)
    logging_err.setLevel(logging.WARNING)

    # root logger, no __name__ as in submodules further down the hierarchy
    global logger
    logger.addHandler(logging_out)
    logger.addHandler(logging_err)
    logger.setLevel(logging.DEBUG)

    logger.info("An INFO message from " + __name__)
    logger.error("An ERROR message from " + __name__)
    sublog.log()

    sys.exit(1)

if __name__ == '__main__':
    main()

output.txt

$ python3 log.py
2017-04-11 09:54:55,316 INFO [log]: An INFO message from __main__
2017-04-11 09:54:55,316 ERROR [log]: An ERROR message from __main__
2017-04-11 09:54:55,316 INFO [sublog]: An INFO message from sublog
2017-04-11 09:54:55,316 ERROR [sublog]: An ERROR message from + sublog

sublog.py

#!/usr/bin/env python3

import logging

logger = logging.getLogger(__name__)

def log():
    logger.info("An INFO message from " + __name__)
    logger.error("An ERROR message from + " + __name__)

Hello @timss
Thank you for your snippets. I turned around the net to understand why a so simple task I was unable to do.
My error was to assign the name name to the logger, without assigning it as global.

Now I endided up with:

main.py

import logging

global logger
logger=logging.getLogger()
logger.setLevel(logging.DEBUG)
file_handler = logging.FileHandler(os.path.join(current_dir,'logs','logfile.log'))
formatter    = logging.Formatter('%(asctime)s : %(levelname)s : %(name)s : %(message)s')
file_handler.setFormatter(formatter)
logger.addHandler(file_handler)
logger.info('started main')

module2.do_something()

module2.py

import logging
logger = logging.getLogger(__name__)
def do_something():
   logger.info('write something')

output

2020-11-05 11:47:30,855 : INFO : root : started main
2020-11-05 11:47:33,915 : INFO : module2 : write something

@MCilento93 Glad to hear it was useful for someone! :)

My pleasure.
Actually even without the global dichiaration it is working 🤗

this helped!

It saved my day!
Thanks