Python Logging Setup

logging_example.py

#!/usr/bin/env python3
import logging
from logging.handlers import RotatingFileHandler
import sys

import colorama

def configure_logging():
    # enable cross-platform colored output
    colorama.init()

    # get the root logger and make it verbose
    logger = logging.getLogger()
    logger.setLevel(logging.DEBUG)

    # this allows us to set an upper threshold for the log levels since the
    # setLevel method only sets a lower one
    class UpperThresholdFilter(logging.Filter):
        def __init__(self, threshold, *args, **kwargs):
            self._threshold = threshold
            super(UpperThresholdFilter, self).__init__(*args, **kwargs)

        def filter(self, rec):
            return rec.levelno <= self._threshold

    # use colored output and use different colors for different levels
    class ColorFormatter(logging.Formatter):
        def __init__(self, colorfmt, *args, **kwargs):
            self._colorfmt = colorfmt
            super(ColorFormatter, self).__init__(*args, **kwargs)

        def format(self, record):
            if record.levelno == logging.INFO:
                color = colorama.Fore.GREEN
            elif record.levelno == logging.WARNING:
                color = colorama.Fore.YELLOW
            elif record.levelno == logging.ERROR:
                color = colorama.Fore.RED
            elif record.levelno == logging.DEBUG:
                color = colorama.Fore.CYAN
            else:
                color = ""
            self._style._fmt = self._colorfmt.format(color, colorama.Style.RESET_ALL)
            return logging.Formatter.format(self, record)

    # configure formatter
    logfmt = "{}[%(asctime)s|%(levelname).3s]{} %(message)s"
    formatter = ColorFormatter(logfmt)

    # configure stdout handler
    stdouthandler = logging.StreamHandler(sys.stdout)
    stdouthandler.setLevel(logging.DEBUG)
    stdouthandler.addFilter(UpperThresholdFilter(logging.INFO))
    stdouthandler.setFormatter(formatter)
    logger.addHandler(stdouthandler)

    # configure stderr handler
    stderrhandler = logging.StreamHandler(sys.stderr)
    stderrhandler.setLevel(logging.WARNING)
    stderrhandler.setFormatter(formatter)
    logger.addHandler(stderrhandler)

    # configure file handler (no colored messages here)
    filehandler = RotatingFileHandler("test.log", maxBytes=1024 * 1024 * 100, backupCount=5)
    filehandler.setLevel(logging.DEBUG)
    filehandler.setFormatter(logging.Formatter(logfmt.format("", "")))
    logger.addHandler(filehandler)


def main(argv):
    configure_logging()
    logging.debug("This is a debug message")
    logging.info("This is an info message")
    logging.warning("This is a warning message")
    logging.error("This is an error message")

    return 0

if __name__ == "__main__":
    sys.exit(main(sys.argv))

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