Python logging formatter with multiple formatters per logging level.

leveled_formatter.py

from logging import getLogger, Formatter, StreamHandler, DEBUG, ERROR


class LeveledFormatter(Formatter):
    _formats = {}

    def __init__(self, *args, **kwargs):
        super(LeveledFormatter, self).__init__(*args, **kwargs)

    def set_formatter(self, level, formatter):
        self._formats[level] = formatter

    def format(self, record):
        f = self._formats.get(record.levelno)

        if f is None:
            f = super(LeveledFormatter, self)

        return f.format(record)


if __name__ == '__main__':
    formatter = LeveledFormatter('??? %(message)s')
    formatter.set_formatter(DEBUG, Formatter('DBG %(message)s'))
    formatter.set_formatter(ERROR, Formatter('ERR %(message)s'))

    handler = StreamHandler()
    handler.setFormatter(formatter)

    logger = getLogger(__name__)
    logger.setLevel(DEBUG)
    logger.addHandler(handler)

    logger.debug('foo')
    logger.info('bar')
    logger.warning('hoge')
    logger.error('piyo')

    # [Output]
    # DBG foo
    # ??? bar
    # ??? hoge
    # ERR piyo