Modifying logging message format based on message logging level in Python3

Question

I asked this question for python 2 here, but bumped into the issue again when the the answer no longer worked for Python 3.2.3.

Here\'s code that works on Python 2.7.3:<

Answer 1

I prefer this because it's shorter, simpler and does not require strings like 'ERROR' to be hard coded. No need to reset ._fmt, because else: can handle that just fine.

Also, using "%(msg)s" doesn't work with lazy logging!

class Formatter(logging.Formatter):
    def format(self, record):
        if record.levelno == logging.INFO:
            self._style._fmt = "%(message)s"
        else:
            self._style._fmt = "%(levelname)s: %(message)s"
        return super().format(record)

Usage example:

import logging

logger = logging.getLogger()
handler = logging.StreamHandler()
handler.setFormatter(Formatter())
logger.setLevel(logging.DEBUG)
logger.addHandler(handler)

logger.debug('foo')
logger.info('bar %d', 4)

DEBUG: foo
bar 4

---

In case you want to have the levelname colored:

class Formatter(logging.Formatter):
    def format(self, record):
        if record.levelno == logging.INFO:
            self._style._fmt = "%(message)s"
        else:
            color = {
                logging.WARNING: 33,
                logging.ERROR: 31,
                logging.FATAL: 31,
                logging.DEBUG: 36
            }.get(record.levelno, 0)
            self._style._fmt = f"\033[{color}m%(levelname)s\033[0m: %(message)s"
        return super().format(record)

see https://en.wikipedia.org/wiki/ANSI_escape_code#3/4_bit for color numbers