Django: Override Debug=True from manage.py runserver command

Question

Is there an easy way to tell Django's runserver to override a single variable in the settings.py file?

I would love to be able to call:

python manage.py runserver 0.0.0.0:8000 Debug=False

Any thoughts?

Motive: have a particular site where there are hundreds of database queries to show or save a particular page, I'd like to be able to turn off debug quickly without having to edit my settings file (which has the possibility of being forgotten).

Answer 1

I think you have two options

The simplest is probably a custom settings override, something like:

# no_debug_settings.py

# pull in the normal settings
from settings import *

# no debug for us
DEBUG = False

Now, when you want to start without debugging, you'd run:

python manage.py runserver --settings=no_debug_settings 0.0.0.0:8000 

As an alternative, you could just customise your manage.py file. That imports settings, and passes it to the execute_manager. If you added some code between the import and the call, you could have it check for extra arguments and alter the settings as needed. It's a bit more fiddly and prone to break / be forgotten, so I'd suggest the override settings wrapper is probably your best way to go.

Answer 2

I edited my settings.py file with a conditional block, like this:

import os  # If needed.

if os.environ.get('DJANGO_DEBUG'):
    print("Debug is enabled.")
    DEBUG = True
    # When not specified, ALLOW_HOSTS defaults to:
    # ALLOWED_HOSTS = ['localhost', '127.0.0.1', '[::1]']
else:
    DEBUG = False
    ALLOWED_HOSTS = ["*"]

Then, run your server by passing the environmental variable DJANGO_DEBUG=1. You can name the variable anything you want so long as you are consistent:

DJANGO_DEBUG=1 python -Wall manage.py runserver

Omit that environmental variable when calling manage.py to disable debug (because setting it to any value, including 0 will still make it true to the Python code.)

Update: A commenter stated that the ALLOWED_HOSTS directive is ignored when DEBUG is True. This is only true in older versions of Django. The current behavior is to honor ALLOWED_HOSTS or default to localhost addresses if it isn't specified when DEBUG is enabled. My answer is updated to reflect this as a minor correction.

This is sourced from the Django documentation:

When DEBUG is True and ALLOWED_HOSTS is empty, the host is validated against ['localhost', '127.0.0.1', '[::1]']

Additionally, it states that the behavior your comment on is now outdated in a few major version lines:

In older versions, ALLOWED_HOSTS wasn’t checked if DEBUG=True. This was also changed in Django 1.10.3, 1.9.11, and 1.8.16 to prevent a DNS rebinding attack.