def __init__(self, log_level=0):
    """Create a sppasLogSetup instance.

    By default, the NullHandler is assigned: no output.
    The numeric values of logging levels are the followings:

        - CRITICAL 	50
        - ERROR 	40
        - WARNING 	30
        - INFO 	    20
        - DEBUG 	10
        - NOTSET 	 0

    Logging messages which are less severe than the given level value
    will be ignored. When NOTSET is assigned, all messages are printed.

    :param log_level: Set the threshold logger value

    """
    self._log_level = int(log_level)
    format_msg = '%(asctime)s [%(levelname)s] %(message)s'
    self._formatter = logging.Formatter(format_msg)
    for h in reversed(list(logging.getLogger().handlers)):
        logging.getLogger().removeHandler(h)
    self._handler = logging.NullHandler()
    logging.getLogger().addHandler(self._handler)
    logging.getLogger().setLevel(self._log_level)

def set_log_level(self, log_level):
    """Fix the log level.

        :param log_level: Set the threshold for the logger

        """
    if log_level == self._log_level:
        return
    self._log_level = int(log_level)
    if self._handler is not None:
        self._handler.setLevel(self._log_level)
    logging.getLogger().setLevel(self._log_level)
    logging.info('Logging set up level={:d}'.format(self._log_level))

def stream_handler(self):
    """Start to redirect to logging StreamHandler.

        """
    self.__stop_handler()
    self._handler = logging.StreamHandler()
    self._handler.setFormatter(self._formatter)
    self._handler.setLevel(self._log_level)
    logging.getLogger().addHandler(self._handler)
    logging.info('Logging redirected to StreamHandler (level={:d}).'.format(self._log_level))

def null_handler(self):
    """Start to redirect to logging NullHandler.

        """
    self.__stop_handler()
    self._handler = logging.NullHandler()
    logging.getLogger().addHandler(self._handler)

def file_handler(self, filename, with_stream=False):
    """Start to redirect to logging FileHandler.

        :param filename: a FileHandler has to be created using this filename.
        :param with_stream: (bool) A StreamHandler is added too.

        """
    self.__stop_handler()
    self._handler = logging.FileHandler(filename, 'a+')
    self._handler.setFormatter(self._formatter)
    self._handler.setLevel(self._log_level)
    logging.getLogger().addHandler(self._handler)
    if with_stream is True:
        console_handler = logging.StreamHandler()
        console_handler.setFormatter(self._formatter)
        console_handler.setLevel(self._log_level)
        logging.getLogger().addHandler(console_handler)
    logging.info('Logging redirected to FileHandler (level={:d}) in file {:s}.'.format(self._log_level, filename))

def __stop_handler(self):
    """Stops the current handler."""
    if self._handler is not None:
        logging.info('Stops current logging handler.')
        logging.getLogger().removeHandler(self._handler)
        for h in reversed(list(logging.getLogger().handlers)):
            logging.getLogger().removeHandler(h)
    self._handler = None