How do I set the Python log level?

Question

Running this

import logging

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

logger.warning("warning")
logger.info("info")
logger.debug("debug")

only prints "warning". I expect it to print all three messages. What am I doing wrong?

I know this should be the most basic thing in the world, but it's got me stumped, and the Python documentation is confusing on this point.

Answer 1

You never called logging.basicConfig() (or something similar) to establish any handlers. As a result, the call to logger.warning calls it for you, which resets the logging level to logging.WARNING . (Technically, the documentation only mentions the module-level functions logging.warning et al. calling logging.basicConfig for you, so I don't know if this explanation is entirely correct. Calling basicConfig does, however, solve the problem.)

import logging

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

logger.warning("warning")
logger.info("info")
logger.debug("debug")

Answer 2

I figured this out almost immediately after asking.

import logging

logging.getLogger(__name__)
logging.basicConfig(level=logging.DEBUG)

logging.warning("warning")
logging.info("info")
logging.debug("debug")

The documentation is confusing because it leaps into the details of logger customization without putting the bare minimum module-level example up front. Hopefully, this post can help correct that.

This is essentially the same question asSet logging levels , but I'm leaving my answer up because it is slightly more minimal than the one there.