Configuration

The default is to log WARNING level to stdout.

Here is a simple config setup from the docs.

logging.basicConfig(filename='example.log', encoding='utf-8', level=logging.DEBUG)

Log levels

  • logging.debug
  • logging.info
  • logging.warning
  • logging.error
  • logging.critical

Variable substitution

Pass literal values to logging message.

logging.info("Hello %s, my name is %", "world", "Joe")

Or variables.

name = 'world'
logging.info("Hello %s", name)

Using extra keyword, based on the docs.

FORMAT = '%(asctime)s %(clientip)-15s %(user)-8s %(message)s'
logging.basicConfig(format=FORMAT)
logger = logging.getLogger('tcpserver')

d = {'clientip': '192.168.0.1', 'user': 'fbloggs'}
logger.warning('Protocol problem: %s', 'connection reset', extra=d)

Would print something like:

2006-02-08 22:20:02,165 192.168.0.1 fbloggs  Protocol problem: connection reset

Built-in variables

See LogRecord attributes in the docs.

Including some like:

  • %(filename)s - name of the current file
  • %(funcName)s - name of the function in current scope
  • %(thread)d - thread ID if available
  • %(threadName)s - thread name if available

Levels

Basic

logger.debug(msg)
logger.info(msg)
logger.error(msg)

Add error trace

logger.exception(msg)

Equivalent to:

logger.error(msg, exc_info=True)

This will log the stack trace of the current error, so you don’t have to add str(e) to your message.

try:
    # ...
except Exception as e:
    logger.exception(msg)