Where does the value for __name__ come from?

Question

So I have a several of django settings files, one for testing, others for different customers.

None of these settings files change sys.path at all.

All of them include a singular base settings file that contains INSTALLED_APPS .

Most of the files have code that does this:

import logging
logger = logging.getLogger(__name__)

logger.error("Something went wrong")

In my test settings files, the module __name__ looks like saml.xyz so the logger.name is saml.xyz but when I use a different settings files, the module __name__ looks like apps.saml.xyz which makes the logger.name apps.saml.xyz .

This causes some log messages to be missed because the handler is connected to the wrong place. A handler for saml.xyz will not get messages for apps.saml.xyz and vice versa. All the routing is based on the configured logger/handler including the apps. portion or not.

So how does python decide which __name__ to give a file, and how could my different settings files affect that __name__ without changing sys.path?

The commands are otherwise identical:

python manage.py test --settings=projectname.test saml

which yields

>>> logger.name
'saml.xyz'

or

python manage.py test --settings=projectname.customer saml

which yields

>>> logger.name
'apps.saml.xyz'

Answer 1

__name__ is the name under which the current module was imported.

If the module was imported with import saml.xyz , __name__ reflects that directly. If you sometimes see apps.saml.xyz then your module was imported using that name, and there are two copies of your module loaded in memory; Python sees the two as separate.

You should avoid importing nested modules; use only the top-level name. Stick to either apps.saml.xyz or saml.xyz , but if the latter must be used, make sure apps/ is not a package and is not itself listed on the python module search path sys.path .