disable_existing_loggers by default in Python logging's dictConfig() is horrible...

terrible_dictConfig_defaults.py

import logging
import logging.config


# A logger that exists before configuration
log_a = logging.getLogger('a')


def f(name, x):
    """Test a logger."""
    log = logging.getLogger(name)
    log.debug('debug from %s: %s', name, x)


# These won't output anything, because logging isn't configured
f('a', 1)
f('b', 2)


def old():
    """Both existing and new loggers work."""
    handler = logging.StreamHandler()
    handler.setLevel(logging.DEBUG)
    handler.setFormatter(logging.Formatter(
        '[%(asctime)s] (%(levelname).1s:%(name)s) %(message)s',
        datefmt='%Y/%m/%d %H:%M:%S',
    ))
    rootlogger = logging.getLogger('')
    rootlogger.addHandler(handler)
    rootlogger.setLevel(logging.DEBUG)

    f('a', 3)
    f('c', 4)


def broken():
    """Seemingly equivalent config, but only new loggers work."""
    logging.config.dictConfig({
        'version': 1,
        'formatters': {
            'default': {
                'format': '[{asctime}] ({levelname[0]}:{name}) {message}',
                #'format': '[%(asctime)s] (%(levelname).1s:%(name)s) %(message)s',
                'datefmt': '%Y/%m/%d %H:%M:%S',
                'style': '{',
            },
        },
        'handlers': {
            'default': {
                'class': 'logging.StreamHandler',
                'level': 'DEBUG',
                'formatter': 'default',
            },
        },
        'root': {
            'level': 'DEBUG',
            'handlers': ['default'],
        },
    })

    f('a', 5)
    f('d', 6)


def fixed():
    """Override the obnoxious default, and now existing and new loggers work again."""
    logging.config.dictConfig({
        'version': 1,
        'formatters': {
            'default': {
                'format': '[{asctime}] ({levelname[0]}:{name}) {message}',
                #'format': '[%(asctime)s] (%(levelname).1s:%(name)s) %(message)s',
                'datefmt': '%Y/%m/%d %H:%M:%S',
                'style': '{',
            },
        },
        'handlers': {
            'default': {
                'class': 'logging.StreamHandler',
                'level': 'DEBUG',
                'formatter': 'default',
            },
        },
        'root': {
            'level': 'DEBUG',
            'handlers': ['default'],
        },
        'disable_existing_loggers': False,
    })

    f('a', 7)
    f('e', 8)


#old()
#broken()
fixed()

Thanks!