Logging function to set up and create a logging object.

loggingExample.py

import logging
import os


def Logger(loggerName, fileName=None, console=False):
    """
    Instantiate a logger object with default Formatter. 
    Default level is set to DEBUG (Show all messages)
    Args:
        loggerName: Name of the logger. Usually __file__ or something sensible.
        fileName: File name of the log file. If ommitted, logger will default to console
        console: Display in console. Only effective when filename is specified.
    Returns:
        Logger Object
    Reference: http://stackoverflow.com/questions/13733552/logger-configuration-to-log-to-file-and-print-to-stdout
    """
    # Set up formatter
    logFormatter = logging.Formatter("%(asctime)s [%(module)s] [%(threadName)-12.12s] [%(levelname)-5.4s] : %(message)s")
    # Create Logger object
    logger = logging.getLogger(loggerName)
    # Set default level
    logger.setLevel(logging.DEBUG)

    if fileName:
        # Add File Handler to logger if fileName is specified
        logFileName = fileName
        
        fileExtAllowed = [".txt", ".log"]
        # Split file and extension
        fileNameWithoutExt, fileExt = os.path.splitext(fileName)
        # Add .log extension if target file does not have the allowed extension
        if not fileExt in fileExtAllowed:
            logFileName = fileName + ".log"
        
        fileHandler = logging.FileHandler(logFileName)
        fileHandler.setFormatter(logFormatter)
        logger.addHandler(fileHandler)

        print "Logging started => {}".format(logFileName)
    else:
        #This is to ensure that logging has at least one Handler.
        console = True


    if console:
        # Add 
        consoleHandler = logging.StreamHandler()
        consoleHandler.setFormatter(logFormatter)
        logger.addHandler(consoleHandler)
    
    return logger

if __name__ == "__main__":
    # Uncomment the different example to test.

    # Example 1 - Console
    logger = Logger("LOG")
    
    # # Example 2 - File
    # logger = Logger("LOG", __file__)

    # # Example 3 - File and Console
    # logger = Logger("LOG", __file__, True)

    # Re-set logger level. 
    # Refer to hierarchy table at https://docs.python.org/2/library/logging.html#logging-levels
    logger.setLevel(logging.DEBUG)

    logger.critical("MY CRITICAL MESSAGE")
    logger.error("MY ERROR MESSAGE")
    logger.warning("MY WARNING MESSAGE")
    logger.info("MY INFO MESSAGE")
    logger.debug("MY DEBUG MESSAGE")