Root logger

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Root logger#

There is a default logger - root logger. This page consiters how you can manipulate with it.

import logging

Note that you can access the root logger just by calling logging.getLogger and manipulate it just like with a regular logger.

logging.getLogger()

<RootLogger root (WARNING)>

Format#

To set up the format for the basic logger, you should use the format parameter of the logging.basicConfig function.

The following example sets up basic logger to print the time of the event and it’s message.

logging.basicConfig(format='%(asctime)s %(message)s')

logging.debug("A DEBUG Message")
logging.info("An INFO")
logging.warning("A WARNING")
logging.error("An ERROR")
logging.critical("A message of CRITICAL severity")

2024-11-20 11:13:36,098 A WARNING
2024-11-20 11:13:36,099 An ERROR
2024-11-20 11:13:36,099 A message of CRITICAL severity

To check format of the basic logger you need:

  • Use logging.getLogger() to get the basic logger;

  • Grab the handler you’re interested in. By default, basic loggers have only one handler;

  • The formatter._fmt field of the handler would be a string defining the format.

The following cell prints the notebooks handler format.

basic_logger = logging.getLogger()
print(basic_logger.handlers[0].formatter._fmt)

%(asctime)s %(message)s

You cannot update the format by calling basicConfig again. The following cell tries to do that:

logging.basicConfig(format="%(levelname)s => %(message)s")
print(basic_logger.handlers[0].formatter._fmt)
logging.error("hello")

2024-11-20 11:13:40,474 hello

%(asctime)s %(message)s

Even a direct _fmt change does not allow to change the output format:

basic_logger.handlers[0].formatter._fmt = "%(levelname)s => %(message)s"
logging.error("hello")

2024-11-20 11:13:42,621 hello
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