setup_logging.py

import logging
import os

SCRIPT_ID = 'name_of_your_script'

logger = logging.getLogger(SCRIPT_ID)

def setup_logging(filename, loglevel='INFO'):
    """
    Set up logging to a file on disk and with a proper log format.
    """

    # If the user that runs the script has access to /var/log (i.e. user is root), log to system-wide logdir
    if os.access('/var/log', os.W_OK):
        logdir = os.path.join('/var/log', SCRIPT_ID)
    # If user doesn't have access to system-wide logdir, log to a file in their home directory instead
    else:
        logdir = os.path.join(os.environ['HOME'], 'logs', SCRIPT_ID)

    logfile = os.path.join(logdir, filename)

    # If logdir doesn't exist, create it
    if not os.path.exists(logdir):
        os.makedirs(logdir)

    loglevel = loglevel.upper()
    supported_loglevels = ['WARNING', 'INFO', 'DEBUG', 'ERROR', 'CRITICAL', 'FATAL']
    if loglevel in supported_loglevels:
        logger.setLevel(getattr(logging, loglevel))
    else:
        raise ValueError('unsupported log level: {}'.format(loglevel))

    # Create file handler to log messages to a file on disk
    fh = logging.FileHandler(logfile)  # By default, file is opened in append mode
    # fh.setLevel(logging.DEBUG)
    fh.setLevel(loglevel)

    # Set log message formatter
    formatter = logging.Formatter('[%(asctime)s] %(levelname)s: %(message)s')
    fh.setFormatter(formatter)

    # Add file handler and log formatter to the logger
    logger.addHandler(fh)