记录器对象不继承根级别

Question

While experimenting with python's logging module, I came across some unexpected behaviour. My guess is that this is due to my misunderstanding, rather than a bug, but I can't figure out what's wrong (and I've been careful to restart the python kernel before testing, to ensure that the root logger is only configured once.

import logging
logging.basicConfig(level=logging.CRITICAL)
logger1 = logging.getLogger(__name__)
logger1.debug("logger1 debug test")

As expected, the logging message is not output.

If I then change the level of the logger as follows:

logger1.setLevel('DEBUG')
logger1.debug("logger1 debug test")

I get the expected output:

DEBUG:__main__:logger1 debug test

However, when I now create a new logger object, it seems to have inherited the properties of logger1, rather than of root:

logger2 = logging.getLogger(__name__)
logger2.debug("logger2 debug test")

which produces:

DEBUG:__main__:logger2 debug test

Weirdly, logger2 still shows the root as the parent, yet shows a level of 10:

print(logger2.__dict__)

{'filters': [], 'name': '__main__', 'level': 10, 'parent': <RootLogger root (CRITICAL)>, 'propagate': True, 'handlers': [], 'disabled': False, '_cache': {10: True}, 'manager': <logging.Manager object at 0x00000265147F2B48>}

Can anyone please explain why logger2 isn't defaulting to a level of 0 (NOTSET)?

Answer 1

Thanks to @Abhinav Mathur for the answer provided in the comments.

The issue was that by attempting to create logger2 with the same name as logger1, I was in effect not creating a new logger object.