Logging setLevel is being ignored

Try running logging.basicConfig() in there. Of note, I see you mention INFO, but use DEBUG. As written, it should show all five messages. Swap out DEBUG with INFO, and you should see four messages.

import logging

logging.basicConfig()
logger = logging.getLogger(__name__)
logger.setLevel(logging.DEBUG)

logger.debug('debug message')
logger.info('info message')
logger.warn('warn message')
logger.error('error message')
logger.critical('critical message')

edit: Do you have logging set up elsewhere in your code already? Can't reproduce the exact behavior you note with the specific code provided.

This is technically also an "answer", because it can "solve" the problem. BUT I definitely DO NOT like it. It is not intuitive, and I lost 2+ hours over it.

Before:

import logging
logger = logging.getLogger('foo')
logger.setLevel(logging.INFO)
logger.info('You can not see me')
# Or you can just use the following one-liner in command line.
# $ python -c "import logging; logger = logging.getLogger('foo'); logger.setLevel(logging.INFO); logger.info('You can not see me')"

After:

import logging

logging.debug('invisible magic')  # <-- magic

logger = logging.getLogger('foo')
logger.setLevel(logging.INFO)
logger.info('But now you can see me')
# Or you can just use the following one-liner in command line.
$ python -c "import logging; logging.debug('invisible magic'); logger = logging.getLogger('foo'); logger.setLevel(logging.INFO); logger.info('But now you see me')"

PS: Comparing it to the current chosen answer, and @Vinay-Sajip's explanation, I can kind of understand why. But still, I wish it was not working that way.

As pointed by some users, using:

logging.basicConfig(level=logging.DEBUG, format='%(message)s')

like written in the accepted answare is not a goot option because it sets the loglevel globally, so it will log debug message from every logger.

In my case the best solution to set log level just for my logger was:

import logging

logger = logging.getLogger('MyLogger')
handler = logging.StreamHandler()
formatter = logging.Formatter('%(asctime)s - %(name)s - %(levelname)s - %(message)s')
handler.setFormatter(formatter)
logger.addHandler(handler)
logger.setLevel(logging.DEBUG)

Not really intuitive solution, but is necessary if you want to set loglevel only for 'MyLogger' and not globally.

Replace the line

logger.setLevel(logging.DEBUG)

with

logging.basicConfig(level=logging.DEBUG, format='%(message)s')

and it should work as expected. If you don't configure logging with any handlers (as in your post - you only configure a level for your logger, but no handlers anywhere), you'll get an internal handler "of last resort" which is set to output just the message (with no other formatting) at the WARNING level.