Python - logging

• Make a logging object.
• Set up two handlers, to log information to a logfile and also the screen during the run.
• Each handler can have a different level (e.g. lots of info, just some info).
• Each handler can also have different formatting for the messages printed.

#!/usr/bin/env python

import logging

log_filename = "log.txt"

# make a logging object
log = logging.getLogger('logger') #inherits from parent - root

# will print info and debug to log file
log.setLevel(logging.DEBUG) 

# set up the two formats for the two handlers

# more detailed message for the log file
file_formatter = logging.Formatter(fmt='%(asctime)s %(levelname)s - %(message)s',
                            datefmt="%Y-%m-%d %H:%M:%S")

# simpler message for the screen
stream_formatter = logging.Formatter(fmt='%(message)s')

# make a file handler object
fh = logging.FileHandler(log_filename, mode='w', encoding='utf-8')
fh.setLevel(logging.DEBUG) #info and debug print to file

# add in the formatting, specified above
fh.setFormatter(file_formatter)

# then add it to the logging object called log
log.addHandler(fh)

# make a stream handler object
ch = logging.StreamHandler()
ch.setLevel(logging.INFO) #just info prints to screen
ch.setFormatter(stream_formatter)
log.addHandler(ch)

# check that info goes to screen AND log file
log.info("logging info here")

# check the debug goes to log file only
log.debug("logging debug here")