Python logging module: Set formatter dynamically

Question

I'm using the python logging module with an YAML config file. In there I define 2 formatters. How can I access these formatters dynamically? I want to overwrite the standard formatter attached to one of my handlers dynamically, if a certain event occurs.

As requested, a small example:

my logging config:

version: 1
disable_existing_loggers: False
formatters:
    console:
        class: colorlog.ColoredFormatter
        format: "%(log_color)s[%(asctime)s] [%(levelname)-8s] --- %(message)s (%(filename)s:%(lineno)s)"
        datefmt: "%Y-%m-%d %H:%M:%S"
    console_user:
        class: colorlog.ColoredFormatter
        format: "%(log_color)s[%(levelname)-8s] --- %(message)s"
handlers:
    console:
        class: logging.StreamHandler
        level: INFO
        formatter: console
        stream: ext://sys.stdout
root:
    level: DEBUG
    handlers: [console]

in my script I have something like:

    import logging
    logging.config.dictConfig(logging_config)
    logger = logging.getLogger()

Now I'd like to do something like

    logger.handlers[0].setFormatter('console_user')

however, there seems to be no reference to any formatters not associated with a handler.

What have you tried? Please edit your question to include a minimal reproducible example — Wayne Werner
– Wayne Werner, Commented Mar 21, 2017 at 19:55

dba · Accepted Answer · 2017-03-21 21:03:28Z

While writing up the example I actually came up with a solution. It's not that nice, since it relies on creating dummy handlers for each formatter not associated with a handler yet, but seems to work.

So, basically for every formatter one could just add a dummy NullHandler, e.g.:

version: 1
disable_existing_loggers: False
formatters:
    simple:
        format: "%(asctime)s - %(name)s - %(levelname)s - %(message)s"
    info:
        format: "[%(asctime)s] [%(levelname)-8s] --- %(message)s (%(filename)s:%(lineno)s)"
        datefmt: "%Y-%m-%d %H:%M:%S"
    console:
        class: colorlog.ColoredFormatter
        format: "%(log_color)s[%(asctime)s] [%(levelname)-8s] --- %(message)s (%(filename)s:%(lineno)s)"
        datefmt: "%Y-%m-%d %H:%M:%S"
    console_user:
        class: colorlog.ColoredFormatter
        format: "%(log_color)s[%(levelname)-8s] --- %(message)s"
handlers:
    console:
        class: logging.StreamHandler
        level: INFO
        formatter: console
        stream: ext://sys.stdout
    dummy:
        class: logging.NullHandler
        formatter: console_user


root:
    level: DEBUG
    handlers: [console, dummy]

and then later on set

logger.handlers[0].setFormatter(logger.handlers[1].formatter)

Ryabchenko Alexander · Accepted Answer · 2020-04-03 10:48:01Z

You cad dynamically create handler with proper formatter and attach it to your logger

logger = logging.getLogger('simple_example')
logger.setLevel(logging.DEBUG)

# create file handler which logs even debug messages
file_handler = logging.FileHandler('spam.log')
file_handler.setLevel(logging.DEBUG)

# create console handler with a higher log level
console_handler = logging.StreamHandler()
console_handler.setLevel(logging.ERROR)

# create formatter and add it to the handlers
formatter = logging.Formatter('%(levelname)s - %(asctime)s - %(name)s: %(message)s')
console_handler.setFormatter(formatter)
file_handler.setFormatter(formatter)

# add the handlers to logger
logger.addHandler(console_handler)
logger.addHandler(file_handler)

# or remove corent handlers and set new
# logger.handlers = [console_handler, file_handler]

Or even change formatter in your logger handler:

formatter = logging.Formatter('%(levelname)s - %(asctime)s - %(name)s: %(message)s')
for handler in my_logger.handers:
    handler.setFormatter(formatter)

# also you may need to do it in logger parent logger
if my_logger.parent
for handler in my_logger.parent.handers:
    handler.setFormatter(formatter)

Collectives™ on Stack Overflow

Python logging module: Set formatter dynamically

2 Answers 2

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related