Logging in Python

python_logging.py

class CustomJsonFormatter(jsonlogger.JsonFormatter):
    """
    Class that helps redefine the log message format
    """
    def add_fields(self, log_record, record, message_dict):
        super(CustomJsonFormatter, self).add_fields(log_record, record, message_dict)
        if not log_record.get('timestamp'):
            # this doesn't use record.created, so it is slightly off
            now = datetime.utcnow().strftime('%Y-%m-%dT%H:%M:%S.%fZ')
            log_record['timestamp'] = now
        if log_record.get('level'):
            log_record['level'] = log_record['level'].lower()
        else:
            log_record['level'] = record.levelname
        if log_record.get('message') is None:
            log_record.pop('message')

# Initialize a logger for readable/debuggable STDOUT
logger = logging.getLogger(__name__)
FORMAT = "[%(filename)s:%(lineno)s - %(funcName)20s() ] %(message)s"
logging.basicConfig(format=FORMAT)

# Add a rotating file handler
fh = RotatingFileHandler('/var/log/flask.log',
                         maxBytes=10000,
                         backupCount=1)

# And have him log in JSON (for consumption by splunk)
fh.setFormatter(CustomJsonFormatter())
logger.addHandler(fh)
logger.setLevel(logging.DEBUG)

This is just my preferred logging setup. You will need the jsonlogger pypi package installed to use it, but if you aren't using the file handler portion, don't worry about it and just leave the class definition out.