/docs/topics/settings.txt

  1===============
  2Django settings
  3===============
  4
  5A Django settings file contains all the configuration of your Django
  6installation. This document explains how settings work and which settings are
  7available.
  8
  9The basics
 10==========
 11
 12A settings file is just a Python module with module-level variables.
 13
 14Here are a couple of example settings::
 15
 16    DEBUG = False
 17    DEFAULT_FROM_EMAIL = 'webmaster@example.com'
 18    TEMPLATE_DIRS = ('/home/templates/mike', '/home/templates/john')
 19
 20Because a settings file is a Python module, the following apply:
 21
 22    * It doesn't allow for Python syntax errors.
 23    * It can assign settings dynamically using normal Python syntax.
 24      For example::
 25
 26          MY_SETTING = [str(i) for i in range(30)]
 27
 28    * It can import values from other settings files.
 29
 30.. _django-settings-module:
 31
 32Designating the settings
 33========================
 34
 35When you use Django, you have to tell it which settings you're using. Do this
 36by using an environment variable, ``DJANGO_SETTINGS_MODULE``.
 37
 38The value of ``DJANGO_SETTINGS_MODULE`` should be in Python path syntax, e.g.
 39``mysite.settings``. Note that the settings module should be on the
 40Python `import search path`_.
 41
 42.. _import search path: http://diveintopython.org/getting_to_know_python/everything_is_an_object.html
 43
 44The django-admin.py utility
 45---------------------------
 46
 47When using :doc:`django-admin.py </ref/django-admin>`, you can either set the
 48environment variable once, or explicitly pass in the settings module each time
 49you run the utility.
 50
 51Example (Unix Bash shell)::
 52
 53    export DJANGO_SETTINGS_MODULE=mysite.settings
 54    django-admin.py runserver
 55
 56Example (Windows shell)::
 57
 58    set DJANGO_SETTINGS_MODULE=mysite.settings
 59    django-admin.py runserver
 60
 61Use the ``--settings`` command-line argument to specify the settings manually::
 62
 63    django-admin.py runserver --settings=mysite.settings
 64
 65.. _django-admin.py: ../django-admin/
 66
 67On the server (mod_wsgi)
 68--------------------------
 69
 70In your live server environment, you'll need to tell your WSGI
 71application what settings file to use. Do that with ``os.environ``::
 72
 73    import os
 74
 75    os.environ['DJANGO_SETTINGS_MODULE'] = 'mysite.settings'
 76
 77Read the :doc:`Django mod_wsgi documentation
 78</howto/deployment/modwsgi>` for more information and other common
 79elements to a Django WSGI application.
 80
 81Default settings
 82================
 83
 84A Django settings file doesn't have to define any settings if it doesn't need
 85to. Each setting has a sensible default value. These defaults live in the
 86module :file:`django/conf/global_settings.py`.
 87
 88Here's the algorithm Django uses in compiling settings:
 89
 90    * Load settings from ``global_settings.py``.
 91    * Load settings from the specified settings file, overriding the global
 92      settings as necessary.
 93
 94Note that a settings file should *not* import from ``global_settings``, because
 95that's redundant.
 96
 97Seeing which settings you've changed
 98------------------------------------
 99
100There's an easy way to view which of your settings deviate from the default
101settings. The command ``python manage.py diffsettings`` displays differences
102between the current settings file and Django's default settings.
103
104For more, see the :djadmin:`diffsettings` documentation.
105
106Using settings in Python code
107=============================
108
109In your Django apps, use settings by importing the object
110``django.conf.settings``. Example::
111
112    from django.conf import settings
113
114    if settings.DEBUG:
115        # Do something
116
117Note that ``django.conf.settings`` isn't a module -- it's an object. So
118importing individual settings is not possible::
119
120    from django.conf.settings import DEBUG  # This won't work.
121
122Also note that your code should *not* import from either ``global_settings`` or
123your own settings file. ``django.conf.settings`` abstracts the concepts of
124default settings and site-specific settings; it presents a single interface.
125It also decouples the code that uses settings from the location of your
126settings.
127
128Altering settings at runtime
129============================
130
131You shouldn't alter settings in your applications at runtime. For example,
132don't do this in a view::
133
134    from django.conf import settings
135
136    settings.DEBUG = True   # Don't do this!
137
138The only place you should assign to settings is in a settings file.
139
140Security
141========
142
143Because a settings file contains sensitive information, such as the database
144password, you should make every attempt to limit access to it. For example,
145change its file permissions so that only you and your Web server's user can
146read it. This is especially important in a shared-hosting environment.
147
148Available settings
149==================
150
151For a full list of available settings, see the :doc:`settings reference </ref/settings>`.
152
153Creating your own settings
154==========================
155
156There's nothing stopping you from creating your own settings, for your own
157Django apps. Just follow these conventions:
158
159    * Setting names are in all uppercase.
160    * Don't reinvent an already-existing setting.
161
162For settings that are sequences, Django itself uses tuples, rather than lists,
163but this is only a convention.
164
165.. _settings-without-django-settings-module:
166
167Using settings without setting DJANGO_SETTINGS_MODULE
168=====================================================
169
170In some cases, you might want to bypass the ``DJANGO_SETTINGS_MODULE``
171environment variable. For example, if you're using the template system by
172itself, you likely don't want to have to set up an environment variable
173pointing to a settings module.
174
175In these cases, you can configure Django's settings manually. Do this by
176calling:
177
178.. function:: django.conf.settings.configure(default_settings, **settings)
179
180Example::
181
182    from django.conf import settings
183
184    settings.configure(DEBUG=True, TEMPLATE_DEBUG=True,
185        TEMPLATE_DIRS=('/home/web-apps/myapp', '/home/web-apps/base'))
186
187Pass ``configure()`` as many keyword arguments as you'd like, with each keyword
188argument representing a setting and its value. Each argument name should be all
189uppercase, with the same name as the settings described above. If a particular
190setting is not passed to ``configure()`` and is needed at some later point,
191Django will use the default setting value.
192
193Configuring Django in this fashion is mostly necessary -- and, indeed,
194recommended -- when you're using a piece of the framework inside a larger
195application.
196
197Consequently, when configured via ``settings.configure()``, Django will not
198make any modifications to the process environment variables (see the
199documentation of :setting:`TIME_ZONE` for why this would normally occur). It's
200assumed that you're already in full control of your environment in these
201cases.
202
203Custom default settings
204-----------------------
205
206If you'd like default values to come from somewhere other than
207``django.conf.global_settings``, you can pass in a module or class that
208provides the default settings as the ``default_settings`` argument (or as the
209first positional argument) in the call to ``configure()``.
210
211In this example, default settings are taken from ``myapp_defaults``, and the
212:setting:`DEBUG` setting is set to ``True``, regardless of its value in
213``myapp_defaults``::
214
215    from django.conf import settings
216    from myapp import myapp_defaults
217
218    settings.configure(default_settings=myapp_defaults, DEBUG=True)
219
220The following example, which uses ``myapp_defaults`` as a positional argument,
221is equivalent::
222
223    settings.configure(myapp_defaults, DEBUG = True)
224
225Normally, you will not need to override the defaults in this fashion. The
226Django defaults are sufficiently tame that you can safely use them. Be aware
227that if you do pass in a new default module, it entirely *replaces* the Django
228defaults, so you must specify a value for every possible setting that might be
229used in that code you are importing. Check in
230``django.conf.settings.global_settings`` for the full list.
231
232Either configure() or DJANGO_SETTINGS_MODULE is required
233--------------------------------------------------------
234
235If you're not setting the ``DJANGO_SETTINGS_MODULE`` environment variable, you
236*must* call ``configure()`` at some point before using any code that reads
237settings.
238
239If you don't set ``DJANGO_SETTINGS_MODULE`` and don't call ``configure()``,
240Django will raise an ``ImportError`` exception the first time a setting
241is accessed.
242
243If you set ``DJANGO_SETTINGS_MODULE``, access settings values somehow, *then*
244call ``configure()``, Django will raise a ``RuntimeError`` indicating
245that settings have already been configured.
246
247Also, it's an error to call ``configure()`` more than once, or to call
248``configure()`` after any setting has been accessed.
249
250It boils down to this: Use exactly one of either ``configure()`` or
251``DJANGO_SETTINGS_MODULE``. Not both, and not neither.
252
253.. _@login_required: ../authentication/#the-login-required-decorator
254