logger.py

import sys
import logging
import logging.handlers

LOG_LEVEL = logging.INFO  # Could be e.g. "INFO", "DEBUG" or "WARNING"

# Make a class we can use to capture stdout and sterr in the log
class MyLogger(object):
    def __init__(self, logger, level):
        """Needs a logger and a logger level."""
        self.logger = logger
        self.level = level

    def write(self, message):
        # Only log if there is a message (not just a new line)
        if message.rstrip() != "":
            self.logger.log(self.level, message.rstrip())

    def flush(self):
        pass


def initLogger(logFileName):
    # Configure logging to log to a file, making a new file at midnight and keeping the last 3 day's data
    # Give the logger a unique name (good practice)
    logger = logging.getLogger(__name__)

    # Set the log level to LOG_LEVEL
    logger.setLevel(LOG_LEVEL)

    # Make a handler that writes to a file, making a new file at midnight and keeping 3 backups
    handler = logging.handlers.TimedRotatingFileHandler(logFileName, when="midnight", backupCount=3)

    # Format each log message like this
    formatter = logging.Formatter('%(asctime)s %(levelname)-8s %(message)s')

    # Attach the formatter to the handler
    handler.setFormatter(formatter)

    # Attach the handler to the logger
    logger.addHandler(handler)

    # Replace stdout with logging to file at INFO level
    sys.stdout = MyLogger(logger, logging.INFO)

    # Replace stderr with logging to file at ERROR level
    sys.stderr = MyLogger(logger, logging.ERROR)