A Django settings file contains all the configuration of your Django installation. This document explains how settings work and which settings are available.
A settings file is just a Python module with module-level variables.
Here are a couple of example settings:
DEBUG = False
DEFAULT_FROM_EMAIL = 'webmaster@example.com'
TEMPLATE_DIRS = ('/home/templates/mike', '/home/templates/john')
Because a settings file is a Python module, the following apply:
It doesn't allow for Python syntax errors.
It can assign settings dynamically using normal Python syntax. For example:
MY_SETTING = [str(i) for i in range(30)]
It can import values from other settings files.
When you use Django, you have to tell it which settings you're using. Do this by using an environment variable, DJANGO_SETTINGS_MODULE.
The value of DJANGO_SETTINGS_MODULE should be in Python path syntax, e.g. mysite.settings. Note that the settings module should be on the Python import search path.
When using django-admin.py, you can either set the environment variable once, or explicitly pass in the settings module each time you run the utility.
Example (Unix Bash shell):
export DJANGO_SETTINGS_MODULE=mysite.settings
django-admin.py runserver
Example (Windows shell):
set DJANGO_SETTINGS_MODULE=mysite.settings
django-admin.py runserver
Use the --settings command-line argument to specify the settings manually:
django-admin.py runserver --settings=mysite.settings
In your live server environment, you'll need to tell Apache/mod_python which settings file to use. Do that with SetEnv:
<Location "/mysite/">
SetHandler python-program
PythonHandler django.core.handlers.modpython
SetEnv DJANGO_SETTINGS_MODULE mysite.settings
</Location>
Read the Django mod_python documentation for more information.
A Django settings file doesn't have to define any settings if it doesn't need to. Each setting has a sensible default value. These defaults live in the module django/conf/global_settings.py.
Here's the algorithm Django uses in compiling settings:
Note that a settings file should not import from global_settings, because that's redundant.
There's an easy way to view which of your settings deviate from the default settings. The command python manage.py diffsettings displays differences between the current settings file and Django's default settings.
For more, see the diffsettings documentation.
In your Django apps, use settings by importing the object django.conf.settings. Example:
from django.conf import settings
if settings.DEBUG:
# Do something
Note that django.conf.settings isn't a module -- it's an object. So importing individual settings is not possible:
from django.conf.settings import DEBUG # This won't work.
Also note that your code should not import from either global_settings or your own settings file. django.conf.settings abstracts the concepts of default settings and site-specific settings; it presents a single interface. It also decouples the code that uses settings from the location of your settings.
You shouldn't alter settings in your applications at runtime. For example, don't do this in a view:
from django.conf import settings
settings.DEBUG = True # Don't do this!
The only place you should assign to settings is in a settings file.
Because a settings file contains sensitive information, such as the database password, you should make every attempt to limit access to it. For example, change its file permissions so that only you and your Web server's user can read it. This is especially important in a shared-hosting environment.
For a full list of available settings, see the settings reference.
There's nothing stopping you from creating your own settings, for your own Django apps. Just follow these conventions:
For settings that are sequences, Django itself uses tuples, rather than lists, but this is only a convention.
In some cases, you might want to bypass the DJANGO_SETTINGS_MODULE environment variable. For example, if you're using the template system by itself, you likely don't want to have to set up an environment variable pointing to a settings module.
In these cases, you can configure Django's settings manually. Do this by calling:
Example:
from django.conf import settings
settings.configure(DEBUG=True, TEMPLATE_DEBUG=True,
TEMPLATE_DIRS=('/home/web-apps/myapp', '/home/web-apps/base'))
Pass configure() as many keyword arguments as you'd like, with each keyword argument representing a setting and its value. Each argument name should be all uppercase, with the same name as the settings described above. If a particular setting is not passed to configure() and is needed at some later point, Django will use the default setting value.
Configuring Django in this fashion is mostly necessary -- and, indeed, recommended -- when you're using a piece of the framework inside a larger application.
Consequently, when configured via settings.configure(), Django will not make any modifications to the process environment variables (see the documentation of TIME_ZONE for why this would normally occur). It's assumed that you're already in full control of your environment in these cases.
If you'd like default values to come from somewhere other than django.conf.global_settings, you can pass in a module or class that provides the default settings as the default_settings argument (or as the first positional argument) in the call to configure().
In this example, default settings are taken from myapp_defaults, and the DEBUG setting is set to True, regardless of its value in myapp_defaults:
from django.conf import settings
from myapp import myapp_defaults
settings.configure(default_settings=myapp_defaults, DEBUG=True)
The following example, which uses myapp_defaults as a positional argument, is equivalent:
settings.configure(myapp_defaults, DEBUG = True)
Normally, you will not need to override the defaults in this fashion. The Django defaults are sufficiently tame that you can safely use them. Be aware that if you do pass in a new default module, it entirely replaces the Django defaults, so you must specify a value for every possible setting that might be used in that code you are importing. Check in django.conf.settings.global_settings for the full list.
If you're not setting the DJANGO_SETTINGS_MODULE environment variable, you must call configure() at some point before using any code that reads settings.
If you don't set DJANGO_SETTINGS_MODULE and don't call configure(), Django will raise an ImportError exception the first time a setting is accessed.
If you set DJANGO_SETTINGS_MODULE, access settings values somehow, then call configure(), Django will raise a RuntimeError indicating that settings have already been configured.
Also, it's an error to call configure() more than once, or to call configure() after any setting has been accessed.
It boils down to this: Use exactly one of either configure() or DJANGO_SETTINGS_MODULE. Not both, and not neither.
Sep 20, 2009