Rotate logfiles each time the application is started (Python)

Question

I\'m using the logging module in Python and I would like it to create a new logfile each time my application is started. The older logfiles shoud be rotated (eg: logfile.txt

Answer 1

I had a similar requirement to be able to force a log rotation at startup based on a command-line option, but for the logfiles to otherwise rotate on their regular schedule. This was my solution:

import logging

from logging.handlers import BaseRotatingHandler
from typing import Union

def rotate_logs(loggers: Union[str,list]=None, delimiter: str=','):
    """Rotate logs.

    Args:
        loggers: List of logger names as list object or as string,
            separated by `delimiter`.

        delimiter: Separator for logger names, if `loggers` is :obj:`str`.
            Defaults to ``,`` (comma).

    """

    # Convert loggers to list.
    if isinstance(loggers, str):
        loggers = [t.strip() for t in loggers.split(delimiter)]

    handlers = []
    root = logging.getLogger()

    # Include root logger in dict.    
    ld = {'': root, **root.manager.loggerDict}

    for k, v in ld.items():
        if loggers is not None and k not in loggers:
            continue

        try:
            for h in v.handlers:
                if (isinstance(h, BaseRotatingHandler) and
                    h not in handlers):

                    handlers.append(h)

        except AttributeError:
            pass

    for h in handlers:
        h.doRollover()



if __name__ == '__main__':
    pass

Notes:

• This has been validated to work if maxBytes > 0 on a RotatingFileHandler.

• This method hasn't been tested with a TimedRotatingFileHandler, but should work.

• This method eliminates the need to maintain a reference to the RotatingFileHandler to be rotated; as a result, it can easily be used when configuring logging using logging.config.