logging demo in python

aux.py

import logging

log = logging.getLogger('my-app.aux')

def log_this(msg):

    if isinstance(msg, int):
        log.debug('{} is an int!'.format(msg))
        return None

    if msg is None:
        log.error('{} is None!'.format(msg))
        return None

    log.info(msg)

main.py

# python logging demo

# logging hierarchy:
#   CRITICAL
#   ERROR
#   WARNING
#   INFO
#   DEBUG
#   NOTSET (*)

import logging

# some random module that also logs stuff
import aux

# create a logger!
log = logging.getLogger('my-app')

# define our minimum default logging level (basically everything)
log.setLevel(logging.DEBUG)

# handler for writing to a file
# (level set to info to reduce unnecessary chatter)
fh = logging.FileHandler('stuff.log')
fh.setLevel(logging.INFO)

# handler for streaming to stdout
# (level set to debug to see everything)
ch = logging.StreamHandler()
ch.setLevel(logging.DEBUG)

# define logging format - here i'm doing some fixed-width formatting stuff
file_formatter = logging.Formatter(
    fmt='%(asctime)s | %(name)-20s | %(levelname)-10s | %(message)s',
)
stdout_formatter = logging.Formatter(
    fmt='%(levelname)-10s | %(message)s',
)

# set the formatting for both outputs
fh.setFormatter(file_formatter)
ch.setFormatter(stdout_formatter)

# add both handlers to our log object
log.addHandler(fh)
log.addHandler(ch)


def main():

    log.info('running main')

    aux.log_this(5)
    aux.log_this('hello')

    # do something that will break
    x = a/5


if __name__ == '__main__':

    try:
        main()
    except:
        # this will also log the traceback
        log.exception('tried running main')
        raise

stuff.log

2017-03-14 15:10:00,562 | my-app               | INFO       | running main
2017-03-14 15:10:00,562 | my-app.aux           | INFO       | hello
2017-03-14 15:10:00,562 | my-app               | ERROR      | tried running main
Traceback (most recent call last):
  File "main.py", line 63, in <module>
    main()
  File "main.py", line 57, in main
    x = a/5
NameError: global name 'a' is not defined