Python Logging - Set Date as Filename

Question

I am working on implementing logging within my Python project and have hit a bit of a snag. I am trying to set up my logging such that the Handlers, and Formatters are all organized into a configuration file. What I am trying to do at the moment is to set up my fileHandler such that it will create a log file that looks something like this: YYYY_MM_DD.log obviously with the Y's representing the year, M's representing the month, and D's representing the day.

This is what I have attempted with my config file:

[loggers]
keys=root,MainLogger

[handlers]
keys=fileHandler, consoleHandler

[formatters]
keys=logFormatter, consoleFormatter

[logger_root]
level=DEBUG
handlers=fileHandler

[logger_MainLogger]
level=DEBUG
handlers=fileHandler, consoleHandler
qualname=MainLogger
propagate=0

[handler_consoleHandler]
class=StreamHandler
level=DEBUG
formatter=consoleFormatter
args=(sys.stdout,)

[handler_fileHandler]
class=FileHandler
level=DEBUG
formatter=logFormatter
args=(datetime.now().strftime('%Y_%m_%d.log'), 'a')

[formatter_logFormatter]
format=%(asctime)s | %(levelname)-8s | %(lineno)04d | %(message)s

[formatter_consoleFormatter]
format=%(asctime)s | %(levelname)-8s | %(fillname)s-%(funcName)s-%(lineno)04d | %message)s

The file I am using to test the configuration is pretty simple:

import logging
import logging.config

logging.config.fileConfig('logging.conf')
logger = logging.getLogger('MainLogger')
logger.debug("TEST")

The specific error I am getting at the moment is:

configparser.InterpolationSyntaxError: '%' must be followed by '%' or '(', found: "%Y_%m_%d.log'), 'a')"

I've tried changing the %Y, %m, and %d as the error says, but that doesn't fix the problem. How do I go about setting up the config file so that my log files look the way I want them to?

I should note when I change the filename to test.log everything worked fine, so this is the only error I seem to be having with this.

Answer 1

Perhaps you can use Python's TimedRotatingFileHandler instead. You can set the interval to create a new log file every day with the date as the suffix.

Documentation--

• Python 2: https://docs.python.org/2/library/logging.handlers.html#timedrotatingfilehandler
• Python 3: https://docs.python.org/3/library/logging.handlers.html#timedrotatingfilehandler

Note that the current day's log file won't have a date. This file handler only adds the date suffix when a new day starts.

Also, the suffix it uses is "%Y-%m-%d", which is a little different than what you want. But there's a SO question here about how you can alter that.