Proper way to import a single Django settings constant to avoid the full settings import overhead?

Question

From Django - Difference between import django.conf.settings and import settings, I understand the accepted way to import the settings file:

from django.conf import settings

I've also read Good or bad practice in Python: import in the middle of a file. One of the answers there takes you to http://mail.python.org/pipermail/python-list/2001-July/699176.html, where points #2 and #4 are relevant to my question.

Let's say I have a huge settings.py and throughout my Django code, I only need to use a "lowly" constant like MEDIA_ROOT in one rarely-called method. So, it seems incredibly wasteful to import the entire settings.py:

from django.conf import settings
...
def foo():
    my_media_root = settings.MEDIA_ROOT

when I can just import the one needed constant:

from settings import MEDIA_ROOT
...
def foo():
    my_media_root = MEDIA_ROOT

and therefore avoid importing the huge settings.py, especially since it may never even be used, if my_media_root is used in only one out of many methods in that file. Of course, this is bad practice, but the "good practice version" of this doesn't work:

from django.conf.settings import MEDIA_ROOT
...
def foo():
    my_media_root = MEDIA_ROOT

as, by design, it causes the expected ImportError: No module named settings exception.

So, my question is, what is the proper way to import just one constant from a large settings.py? Thanks in advance.

Answer 1

If this is a Django project, then the settings file has already been imported, it doesn't cost you anything to simply import it and use the constant you want. Importing a module many times in Python only executes the file once.

The usual way to import settings:

from django.conf import settings

This just assigns one name in your module (settings) to the value of an existing already-imported settings object. It's equivalent to, and has about the same execution time as:

settings = sys.modules['django.conf'].settings

Have you found problems doing it the simple way?