Change level logged to IPython/Jupyter notebook

Question

I have a package that relies on several different modules, each of which sets up its own logger. That allows me to log where each log message originates from, which is useful.

However, when using this code in an IPython/Jupyter notebook, I was having trouble controlling what got printed to the screen. Specifically, I was getting a lot of DEBUG-level messages that I didn't want to see.

How do I change the level of logs that get printed to the notebook?

More info:

I've tried to set up a root logger in the notebook as follows:

# In notebook
import logging
logging.basicConfig()
logger = logging.getLogger()
logger.setLevel(logging.INFO)
# Import the module
import mymodule

And then at the top of my modules, I have

# In mymodule.py
import logging
logger = logging.getLogger('mypackage.' + __name__)
logger.setLevel(logging.DEBUG)
logger.propagate = True
# Log some messages
logger.debug('debug')
logger.info('info')

When the module code is called in the notebook, I would expect the logs to get propagated up, and then for the top logger to only print the info log statement. But both the debug and the info log statement get shown.

Related links:

• From this IPython issue, it seems that there are two different levels of logging that one needs to be aware of. One, which is set in the ipython_notebook_config file, only affects the internal IPython logging level. The other is the IPython logger, accessed with get_ipython().parent.log.
• https://github.com/ipython/ipython/issues/8282
• https://github.com/ipython/ipython/issues/6746

Answer 1

The root cause of this issue (from https://github.com/ipython/ipython/issues/8282) is that the Notebook creates a root logger by default (which is different from IPython default behavior!). The solution is to get at the handler of the notebook logger, and set its level:

# At the beginning of the notebook
import logging
logger = logging.getLogger()
assert len(logger.handlers) == 1
handler = logger.handlers[0]
handler.setLevel(logging.INFO)

With this, I don't need to set logger.propagate = True in the modules and it works.