ColorizedStreamHandler.py

#!/usr/bin/env python3

import collections
import logging
import sys
import os


class ColorizedStreamHandler(logging.StreamHandler):
    def __init__(self):
        super().__init__()

        # we define color here for custom color palettes per instance
        Color = collections.namedtuple('Color', [
            'BLACK', 'RED', 'GREEN', 'YELLOW',
            'BLUE', 'MAGENTA', 'CYAN', 'WHITE',
            'BLACK_BOLD', 'RED_BOLD', 'GREEN_BOLD', 'YELLOW_BOLD',
            'BLUE_BOLD', 'MAGENTA_BOLD', 'CYAN_BOLD', 'WHITE_BOLD'])

        # octal ansi color values (0, 255)
        self.ForegroundColor = Color(*map(lambda x: f'\33[38;5;{x}m', range(16)))
        self.BackgroundColor = Color(*map(lambda x: f'\33[48;5;{x}m', range(16)))
        self.RESET = '\33[0m'
        self.LOG_LEVEL = {
            logging.CRITICAL: (self.BackgroundColor.RED_BOLD + self.ForegroundColor.WHITE_BOLD),
            logging.ERROR: self.ForegroundColor.RED_BOLD,
            logging.WARNING: self.ForegroundColor.YELLOW_BOLD,
            logging.INFO: self.ForegroundColor.BLUE_BOLD,
            logging.DEBUG: self.RESET,
            logging.NOTSET: self.RESET
        }

    def emit(self, record):
        try:
            message = self.format(record)
            if ColorizedStreamHandler.supports_color():
                color = self.LOG_LEVEL.get(record.levelno)
                message = f'{color}{message}{self.RESET}'

            self.stream.write(message)
            self.stream.write(self.terminator)
            self.flush()
        except (KeyboardInterrupt, SystemExit):
            raise
        except (Exception):
            self.handleError(record)

    @staticmethod
    def supports_color():
        '''
        Returns True if the running system's terminal supports color, and False
        otherwise.

        Extracted from Django: https://git.io/JJ7zX
        '''
        supported_platform = sys.platform != 'win32' or 'ANSICON' in os.environ

        # isatty is not always implemented, #6223.
        is_a_tty = hasattr(sys.stdout, 'isatty') and sys.stdout.isatty()
        return supported_platform and is_a_tty

    def color_test(self):
        print(f'{"-" * 10} PALETTE TEST {"-" * 10}')
        ForegroundColor = self.ForegroundColor
        BackgroundColor = self.BackgroundColor
        columns = zip(zip(ForegroundColor._fields, ForegroundColor),
                      zip(BackgroundColor._fields, BackgroundColor))
        for left, right in columns:
            left = f'{left[1]}{left[0]:14}{self.RESET}'
            right = f'{right[1]}{right[0]:14}{self.RESET}'
            print(f'  {left}{right}{self.RESET}')


if __name__ == '__main__':
    logger = logging.getLogger(__name__)

    colorizer = ColorizedStreamHandler()
    colorizer.setFormatter(logging.Formatter(
            fmt='%(asctime)s.%(msecs)03d [%(levelname)8s] - %(message)s',
            datefmt='%Y-%m-%d %H:%M:%S'))
    colorizer.setLevel(logging.DEBUG)
    logger.addHandler(colorizer)
    logger.setLevel(logging.DEBUG)

    colorizer.color_test()
    for level in colorizer.LOG_LEVEL:
        logger.log(level, f'logging example for {level}')