Single function #logging #python

single_function_logging.py

def get_logger():
    """
    Returns a logger object that can directly be used.

    It is a single function singleton,
    it returns the same object each time it is called.

    Do not forget to change:
    logger_name = "defaultlogger"
    logger_file_path = "log1.log"

    Example:
        import logging

        logger = get_logger()

        logger.debug('debug message')
        logger.info('info message')
        logger.warn('warn message')
        logger.error('error message')
        logger.critical('critical message')
    """

    logger_name = "defaultlogger"
    logger_file_path = "log1.log"

    if not hasattr(get_logger, "static_logger_instance"):
        # In Python, each function is an object.
        # That means, get_logger is an object.
        # This part of the code adds a member to the object
        # if it does not exist yet.
        get_logger.static_logger_instance = None

    logger = None
    if get_logger.static_logger_instance == None:
        logger = logging.getLogger(logger_name)

        logger.setLevel(logging.DEBUG)

        # the logger to write to screen.
        logger_stream_handler = logging.StreamHandler()

        # the logger to write to file.
        logger_file_handler = logging.FileHandler(logger_file_path)

        logger_format = "%(levelname)s %(asctime)s "
        logger_format = logger_format + "%(funcName)s %(lineno)d %(message)s"
        logger_formatter = logging.Formatter(logger_format)

        logger_stream_handler.setFormatter(logger_formatter)
        logger_file_handler.setFormatter(logger_formatter)

        logger.addHandler(logger_stream_handler)
        logger.addHandler(logger_file_handler)

        get_logger.static_logger_instance = logger
    else:
        # returns the previous logger that has been already declared.
        logger = get_logger.static_logger_instance

    return logger


if __name__ == '__main__':
    import logging

    logger = get_logger()

    logger.debug('debug message')
    logger.info('info message')
    logger.warn('warn message')
    logger.error('error message')
    logger.critical('critical message')