Refer to Rust `env_logger`

env_logger.py

import logging
import os


class ColoredFormatter(logging.Formatter):
    def __init__(self, coloring=True, fmt='%(L)s{asctime} {levelname:<%(T)s} {name}%(R)s {message}',
                 datefmt = '%Y-%m-%dT%H:%M:%SZ', style = '{', *args, **kwargs):
        if coloring:
            L, R = map('\033[90m{}\033[m'.format, '[]')
            T = 15
        else:
            L, R = '[]'
            T = 5
        
        super().__init__(fmt=fmt%locals(), datefmt=datefmt, style=style, *args, **kwargs)
        self.coloring = coloring

    def format(self, record):
        if self.coloring:
            # NOTE: Keep ASCII code be the same length (except CRITICAL) in order to format alignment.
            if record.levelname == 'CRITICAL':
                record.levelname = f'\033[1;4;5;7;35mCRITICAL\033[m'
            elif record.levelname == 'ERROR':
                record.levelname = f'\033[1;31mERROR\033[m'
            elif record.levelname == 'WARNING':
                record.levelname = f'\033[0;33mWARN\033[m'
            elif record.levelname == 'INFO':
                record.levelname = f'\033[0;32mINFO\033[m'
            elif record.levelname == 'DEBUG':
                record.levelname = f'\033[0;34mDEBUG\033[m'
            elif record.levelname == 'TRACE':
                record.levelname = f'\033[0;36mTRACE\033[m'
            else:
                pass

        return super().format(record)


def register_trace(logging, trace_level=5):
    """
    Register logging to support `TRACE` level.
    """
    def trace(self, msg, *args, **kwargs):
        if self.isEnabledFor(trace_level):
            self._log(trace_level, msg, args, **kwargs)

    logging.TRACE = trace_level
    logging.addLevelName(trace_level, 'TRACE')
    logging.Logger.trace = trace


def init(var_name='LOGGING'):
    """
    Initialize `env_logger` including:

    * registering trace level
    * coloring if destination is a TTY
    * reading environment variable for config
    """
    register_trace(logging)

    stream_handler = logging.StreamHandler()
    stream_handler.setFormatter(ColoredFormatter(
        coloring = 'TERM' in os.environ and stream_handler.stream.isatty()
    ))

    # NOTE: To keep it simple, now the config only support a level name for root logger.
    logging_config = os.getenv(var_name, '').strip()
    levelname = logging_config.upper()
    if (level := getattr(logging, levelname, None)) is None:
        logger = logging.getLogger()
        logger.addHandler(stream_handler)
    else:
        logger = logging.getLogger()
        logger.setLevel(level)
        logger.addHandler(stream_handler)


if __name__ == '__main__':
    init()

    logger = logging.getLogger()
    logger.critical('message')
    logger.error('message')
    logger.warning('message')
    logger.info('message')
    logger.debug('message')
    logger.trace('message')