logging.py 文件源码

def create_logger(app):
    """Creates a logger for the given application.  This logger works
    similar to a regular Python logger but changes the effective logging
    level based on the application's debug flag.  Furthermore this
    function also removes all attached handlers in case there was a
    logger with the log name before.
    """
    Logger = getLoggerClass()

    class DebugLogger(Logger):
        def getEffectiveLevel(x):
            if x.level == 0 and app.debug:
                return DEBUG
            return Logger.getEffectiveLevel(x)

    class DebugHandler(StreamHandler):
        def emit(x, record):
            StreamHandler.emit(x, record) if app.debug else None

    handler = DebugHandler()
    handler.setLevel(DEBUG)
    handler.setFormatter(Formatter(app.debug_log_format))
    logger = getLogger(app.logger_name)
    # just in case that was not a new logger, get rid of all the handlers
    # already attached to it.
    del logger.handlers[:]
    logger.__class__ = DebugLogger
    logger.addHandler(handler)
    return logger