python - Logging setLevel is being ignored

Question

The below code is copied from the documentation. I am supposed to be able to see all the info logs. But I don't. I am only able to see the warn and above even though I've set setLevel to INFO.

Why is this happening? foo.py:

import logging

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')

Output:

workingDirectory$ python foo.py
warn message
error message
critical message

Where did the info and debug messages go??

Answer 1

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.