django1/docs/settings.txt

===============
Django settings
===============

A Django settings file contains all the configuration of your Django
installation. This document explains how settings work and which settings are
available.

The basics
==========

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 shouldn't have 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.

Designating the settings
========================

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.
``"myproject.settings.main"``. Note that the settings module should be on the
Python `import search path`_.

.. _import search path: http://diveintopython.org/getting_to_know_python/everything_is_an_object.html

The django-admin.py utility
---------------------------

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=myproject.settings.main
    django-admin.py runserver

Example (Windows shell)::

    set DJANGO_SETTINGS_MODULE=myproject.settings.main
    django-admin.py runserver

Use the ``--settings`` command-line argument to specify the settings manually::

    django-admin.py runserver --settings=myproject.settings.main

.. _django-admin.py: http://www.djangoproject.com/documentation/django_admin/

On the server (mod_python)
--------------------------

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 myproject.settings.main
    </Location>

Read the `Django mod_python documentation`_ for more information.

.. _Django mod_python documentation: http://www.djangoproject.com/documentation/mod_python/

Default settings
================

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 file
``django/conf/global_settings.py``.

Here's the algorithm Django uses in compiling settings:

    * Load settings from ``global_settings.py``.
    * Load settings from the specified settings file, overriding the global
      settings as necessary.

Note that a settings file should *not* import from ``global_settings``, because
that's redundant.

Using settings in Python code
=============================

In your Django apps, use settings by importing them from
``django.conf.settings``. Example::

    from django.conf.settings import DEBUG

    if DEBUG:
        # Do something

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.

Altering settings at runtime
============================

You shouldn't alter settings in your applications at runtime. For example,
don't do this in a view::

    from django.conf.settings import DEBUG

    DEBUG = True   # Don't do this!

The only place you should assign to settings is in a settings file.

Security
========

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.

Available settings
==================

Here's a full list of all available settings, in alphabetical order, and their
default values.

ABSOLUTE_URL_OVERRIDES
----------------------

Default: ``{}`` (Empty dictionary)

A dictionary mapping ``"app_label.module_name"`` strings to functions that take
a model object and return its URL. This is a way of overriding
``get_absolute_url()`` methods on a per-installation basis. Example::

    ABSOLUTE_URL_OVERRIDES = {
        'blogs.blogs': lambda o: "/blogs/%s/" % o.slug,
        'news.stories': lambda o: "/stories/%s/%s/" % (o.pub_year, o.slug),
    }

ADMIN_FOR
---------

Default: ``()`` (Empty list)

Used for admin-site settings modules, this should be a tuple of settings
modules (in the format ``'foo.bar.baz'``) for which this site is an admin.

ADMIN_MEDIA_PREFIX
------------------

Default: ``'/media/'``

The URL prefix for admin media -- CSS, JavaScript and images. Make sure to use
a trailing slash.

ADMINS
------

Default: ``()`` (Empty tuple)

A tuple that lists people who get code error notifications. When
``DEBUG=False`` and a view raises an exception, Django will e-mail these people
with the full exception information. Each member of the tuple should be a tuple
of (Full name, e-mail address). Example::

    (('John', 'john@example.com'), ('Mary', 'mary@example.com'))

ALLOWED_INCLUDE_ROOTS
---------------------

Default: ``()`` (Empty tuple)

A tuple of strings representing allowed prefixes for the ``{% ssi %}`` template
tag. This is a security measure, so that template authors can't access files
that they shouldn't be accessing.

For example, if ``ALLOWED_INCLUDE_ROOTS`` is ``('/home/html', '/var/www')``,
then ``{% ssi /home/html/foo.txt %}`` would work, but ``{% ssi /etc/passwd %}``
wouldn't.

APPEND_SLASH
------------

Default: ``True``

Whether to append trailing slashes to URLs. This is only used if
``CommonMiddleware`` is installed (see the `middleware docs`_). See also
``PREPEND_WWW``.

CACHE_BACKEND
-------------

Default: ``'simple://'``

The cache backend to use. See the `cache docs`_.

CACHE_MIDDLEWARE_KEY_PREFIX

Default: ``''`` (Empty string)

The cache key prefix that the cache middleware should use. See the
`cache docs`_.

DATABASE_ENGINE
---------------

Default: ``'postgresql'``

Which database backend to use. Either ``'postgresql'``, ``'mysql'``,
``'sqlite3'`` or ``'ado_mssql'``.

DATABASE_HOST
-------------

Default: ``''`` (Empty string)

Which host to use when connecting to the database. An empty string means
localhost. Not used with SQLite.

DATABASE_NAME
-------------

Default: ``''`` (Empty string)

The name of the database to use. For SQLite, it's the full path to the database
file.

DATABASE_PASSWORD
-----------------

Default: ``''`` (Empty string)

The password to use when connecting to the database. Not used with SQLite.

DATABASE_PORT
-------------

Default: ``''`` (Empty string)

The port to use when connecting to the database. An empty string means the
default port. Not used with SQLite.

DATABASE_USER
-------------

Default: ``''`` (Empty string)

The username to use when connecting to the database. Not used with SQLite.

DEBUG
-----

Default: ``False``

A boolean that turns on/off debug mode.

DEFAULT_CHARSET
---------------

Default: ``'utf-8'``

Default charset to use for all ``HttpResponse`` objects, if a MIME type isn't
manually specified. Used with ``DEFAULT_CONTENT_TYPE`` to construct the
``Content-Type`` header.

DEFAULT_CONTENT_TYPE
--------------------

Default: ``'text/html'``

Default content type to use for all ``HttpResponse`` objects, if a MIME type
isn't manually specified. Used with ``DEFAULT_CHARSET`` to construct the
``Content-Type`` header.

DEFAULT_FROM_EMAIL
------------------

Default: ``'webmaster@localhost'``

Default e-mail address to use for various automated correspondence from the
site manager(s).

DISALLOWED_USER_AGENTS
----------------------

Default: ``()`` (Empty tuple)

List of compiled regular expression objects representing User-Agent strings
that are not allowed to visit any page, systemwide. Use this for bad
robots/crawlers.  This is only used if ``CommonMiddleware`` is installed (see
the `middleware docs`_).

EMAIL_HOST
----------

Default: ``'localhost'``

The host to use for sending e-mail.

EMAIL_SUBJECT_PREFIX
--------------------

Default: ``'[Django] '``

Subject-line prefix for e-mail messages sent with ``django.core.mail.mail_admins``
or ``django.core.mail.mail_managers``. You'll probably want to include the
trailing space.

IGNORABLE_404_ENDS
------------------

Default: ``('mail.pl', 'mailform.pl', 'mail.cgi', 'mailform.cgi', 'favicon.ico', '.php')``

See also ``IGNORABLE_404_STARTS``.

IGNORABLE_404_STARTS
--------------------

Default: ``('/cgi-bin/', '/_vti_bin', '/_vti_inf')``

A tuple of strings that specify beginnings of URLs that should be ignored by
the 404 e-mailer. See ``SEND_BROKEN_LINK_EMAILS`` and ``IGNORABLE_404_ENDS``.

INTERNAL_IPS
------------

Default: ``()`` (Empty tuple)

A tuple of IP addresses, as strings, that:

    * See debug comments, when ``DEBUG`` is ``True``
    * Receive X headers if the ``XViewMiddleware`` is installed (see the
      `middleware docs`_)

JING_PATH
---------

Default: ``'/usr/bin/jing'``

Path to the "Jing" executable. Jing is a RELAX NG validator, and Django uses it
to validate each ``XMLField`` in your models.
See http://www.thaiopensource.com/relaxng/jing.html .

LANGUAGE_CODE
-------------

Default: ``'en-us'``

A string representing the language code for this installation.

MANAGERS
--------

Default: ``ADMINS`` (Whatever ``ADMINS`` is set to)

A tuple in the same format as ``ADMINS`` that specifies who should get
broken-link notifications when ``SEND_BROKEN_LINK_EMAILS=True``.

MEDIA_ROOT
----------

Default: ``''`` (Empty string)

Absolute path to the directory that holds media for this installation.
Example: ``"/home/media/media.lawrence.com/"`` See also ``MEDIA_URL``.

MEDIA_URL
---------

Default: ``''`` (Empty string)

URL that handles the media served from ``MEDIA_ROOT``.
Example: ``"http://media.lawrence.com"``

MIDDLEWARE_CLASSES
------------------

Default: ``("django.middleware.sessions.SessionMiddleware", "django.middleware.common.CommonMiddleware", "django.middleware.doc.XViewMiddleware")``

A tuple of middleware classes to use. See the `middleware docs`_.

PREPEND_WWW
-----------

Default: ``False``

Whether to prepend the "www." subdomain to URLs that don't have it. This is
only used if ``CommonMiddleware`` is installed (see the `middleware docs`_).
See also ``PREPEND_WWW``.

SECRET_KEY
----------

Default: ``''`` (Empty string)

A secret key for this particular Django installation. Used to provide a seed in
secret-key hashing algorithms. Set this to a random string -- the longer, the
better. ``django-admin.py startproject`` creates one automatically.

SEND_BROKEN_LINK_EMAILS
-----------------------

Default: ``False``

Whether to send an e-mail to the ``MANAGERS`` each time somebody visits a
Django-powered page that is 404ed with a non-empty referer (i.e., a broken
link). This is only used if ``CommonMiddleware`` is installed (see the
`middleware docs`_). See also ``IGNORABLE_404_STARTS`` and
``IGNORABLE_404_ENDS``.

SERVER_EMAIL
------------

Default: ``'root@localhost'``

The e-mail address that error messages come from, such as those sent to
``ADMINS`` and ``MANAGERS``.

SESSION_COOKIE_AGE
------------------

Default: ``1209600`` (2 weeks, in seconds)

The age of session cookies, in seconds. See the `session docs`_.

SESSION_COOKIE_DOMAIN
---------------------

Default: ``None``

The domain to use for session cookies. Set this to a string such as
``".lawrence.com"`` for cross-domain cookies, or use ``None`` for a standard
domain cookie. See the `session docs`_.

SESSION_COOKIE_NAME
-------------------

Default: ``'hotclub'``

The name of the cookie to use for sessions. This can be whatever you want.
See the `session docs`_.

``'hotclub'`` is a reference to the Hot Club of France, the band Django
Reinhardt played in.

TEMPLATE_DIRS
-------------

Default: ``()`` (Empty tuple)

List of locations of the template source files, in search order. See the
`template documentation`_.

TEMPLATE_FILE_EXTENSION
-----------------------

Default: ``'.html'``

The file extension to append to all template names when searching for
templates. See the `template documentation`_.

TEMPLATE_LOADERS
----------------

Default: ``('django.core.template.loaders.filesystem.load_template_source',)``

A tuple of callables (as strings) that know how to import templates from
various sources. See the `template documentation`_.

TIME_ZONE
---------

Default: ``'America/Chicago'``

A string representing the time zone for this installation.
`See available choices`_.

USE_ETAGS
---------

Default: ``False``

A boolean that specifies whether to output the "Etag" header. This saves
bandwidth but slows down performance. This is only used if ``CommonMiddleware``
is installed (see the `middleware docs`_).

USE_FLAT_PAGES
--------------

Default: ``True``

Whether to check the flat-pages table as a last resort for all 404 errors. This
is only used if ``CommonMiddleware`` is installed (see the `middleware docs`_).

.. _cache docs: http://www.djangoproject.com/documentation/cache/
.. _middleware docs: http://www.djangoproject.com/documentation/middleware/
.. _session docs: http://www.djangoproject.com/documentation/sessions/
.. _See available choices: http://www.postgresql.org/docs/current/static/datetime-keywords.html#DATETIME-TIMEZONE-SET-TABLE
.. _template documentation: http://www.djangoproject.com/documentation/templates_python/

Creating your own settings
==========================

There's nothing stopping you from creating your own settings, for your own
Django apps. Just follow these conventions:

    * Setting names are in all uppercase.
    * For settings that are sequences, use tuples instead of lists. This is
      purely for performance.
    * Don't reinvent an already-existing setting.