Can Python’s logging format be modified depending on the message log level?

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I just ran into this issue and had trouble filling in the “holes” left in the above example. Here’s a more complete, working version that I used. Hopefully this helps someone:

# Custom formatter
class MyFormatter(logging.Formatter):

    err_fmt  = "ERROR: %(msg)s"
    dbg_fmt  = "DBG: %(module)s: %(lineno)d: %(msg)s"
    info_fmt = "%(msg)s"


    def __init__(self, fmt="%(levelno)s: %(msg)s"):
        logging.Formatter.__init__(self, fmt)


    def format(self, record):

        # Save the original format configured by the user
        # when the logger formatter was instantiated
        format_orig = self._fmt

        # Replace the original format with one customized by logging level
        if record.levelno == logging.DEBUG:
            self._fmt = MyFormatter.dbg_fmt

        elif record.levelno == logging.INFO:
            self._fmt = MyFormatter.info_fmt

        elif record.levelno == logging.ERROR:
            self._fmt = MyFormatter.err_fmt

        # Call the original formatter class to do the grunt work
        result = logging.Formatter.format(self, record)

        # Restore the original format configured by the user
        self._fmt = format_orig

        return result

Edit:

Compliments of Halloleo, here’s an example of how to use the above in your script:

fmt = MyFormatter()
hdlr = logging.StreamHandler(sys.stdout)

hdlr.setFormatter(fmt)
logging.root.addHandler(hdlr)
logging.root.setLevel(DEBUG)

Edit 2:

Python3 logging has changed a bit. See here for a Python3 approach.

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