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Appendix D: Settings

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

What's a Settings File?

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 must be valid Python code; syntax errors aren't allowed.

  • 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.

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.

Seeing Which Settings You've Changed

There's an easy way to view which of your settings deviate from the default settings. The command manage.py diffsettings displays differences between the current settings file and Django's default settings.

manage.py is described in more detail in Appendix F.

Using Settings in Python Code

In your Django applications, use settings by importing the object django.conf.settings, for 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.

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 import settings

settings.DEBUG = True   # Don't do this!

The only place that settings should be defined in is 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.

Creating Your Own Settings

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

  • Use all uppercase for setting names.
  • For settings that are sequences, use tuples instead of lists. Settings should be considered immutable and shouldn't be changed once they're defined. Using tuples mirrors these semantics.
  • Don't reinvent an already existing setting.

Designating the Settings: DJANGO_SETTINGS_MODULE

When you use Django, you have to tell it which settings you're using. Do this by using the 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 (PYTHONPATH).

The django-admin.py Utility

When using django-admin.py (see Appendix F), you can either set the environment variable once or explicitly pass in the settings module each time you run the utility.

Here's an example using the Unix Bash shell:

export DJANGO_SETTINGS_MODULE=mysite.settings
django-admin.py runserver

Here's an example using the 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

The manage.py utility created by startproject as part of the project skeleton sets DJANGO_SETTINGS_MODULE automatically; see Appendix F for more about manage.py.

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 mysite.settings
</Location>

For more information, read the Django mod_python documentation online at http://docs.djangoproject.com/en/dev/howto/deployment/modpython/.

Using Settings Without Setting DJANGO_SETTINGS_MODULE

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 django.conf.settings.configure(). Here's an 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 earlier. 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 explanation of TIME_ZONE later in this appendix for why this would normally occur.) It's assumed that you're already in full control of your environment in these cases.

Custom Default Settings

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.

Either configure() or DJANGO_SETTINGS_MODULE Is Required

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 EnvironmentError exception the first time a setting is accessed.

If you set DJANGO_SETTINGS_MODULE, access settings values somehow, and then call configure(), Django will raise an EnvironmentError stating 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, and only once.

Available Settings

The following sections consist of a list of the main available settings, in alphabetical order, and their default values.

ABSOLUTE_URL_OVERRIDES

Default: {} (empty dictionary)

This is a dictionary mapping "app_label.model_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. Here's an example:

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

Note that the model name used in this setting should be all lowercase, regardless of the case of the actual model class name.

ADMIN_MEDIA_PREFIX

Default: '/media/'

This setting is the URL prefix for admin media: CSS, JavaScript, and images. Make sure to use a trailing slash.

ADMINS

Default: () (empty tuple)

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

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

Note that Django will email all of these people whenever an error happens.

ALLOWED_INCLUDE_ROOTS

Default: () (empty tuple)

This is 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

This setting indicates whether to append trailing slashes to URLs. This is used only if CommonMiddleware is installed (see Chapter 17). See also PREPEND_WWW.

CACHE_BACKEND

Default: 'locmem://'

This is the cache back-end to use (see Chapter 15).

CACHE_MIDDLEWARE_KEY_PREFIX

Default: '' (empty string)

This is the cache key prefix that the cache middleware should use (see Chapter 15).

DATABASE_ENGINE

Default: '' (empty string)

This setting indicates which database back-end to use, e.g. 'postgresql_psycopg2', or 'mysql'.

DATABASE_HOST

Default: '' (empty string)

This setting indicates which host to use when connecting to the database. An empty string means localhost. This is not used with SQLite.

If this value starts with a forward slash ('/') and you're using MySQL, MySQL will connect via a Unix socket to the specified socket:

DATABASE_HOST = '/var/run/mysql'

If you're using MySQL and this value doesn't start with a forward slash, then this value is assumed to be the host.

DATABASE_NAME

Default: '' (empty string)

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

DATABASE_OPTIONS

Default: {} (empty dictionary)

This is extra parameters to use when connecting to the database. Consult the back-end module's document for available keywords.

DATABASE_PASSWORD

Default: '' (empty string)

This setting is the password to use when connecting to the database. It is not used with SQLite.

DATABASE_PORT

Default: '' (empty string)

This is the port to use when connecting to the database. An empty string means the default port. It is not used with SQLite.

DATABASE_USER

Default: '' (empty string)

This setting is the username to use when connecting to the database. It is not used with SQLite.

DATE_FORMAT

Default: 'N j, Y' (e.g., Feb. 4, 2003)

This is the default formatting to use for date fields on Django admin change-list pages -- and, possibly, by other parts of the system. It accepts the same format as the now tag (see Appendix E, Table E-2).

See also DATETIME_FORMAT, TIME_FORMAT, YEAR_MONTH_FORMAT, and MONTH_DAY_FORMAT.

DATETIME_FORMAT

Default: 'N j, Y, P' (e.g., Feb. 4, 2003, 4 p.m.)

This is the default formatting to use for datetime fields on Django admin change-list pages -- and, possibly, by other parts of the system. It accepts the same format as the now tag (see Appendix E, Table E-2).

See also DATE_FORMAT, DATETIME_FORMAT, TIME_FORMAT, YEAR_MONTH_FORMAT, and MONTH_DAY_FORMAT.

DEBUG

Default: False

This setting is a Boolean that turns debug mode on and off.

If you define custom settings, django/views/debug.py has a HIDDEN_SETTINGS regular expression that will hide from the DEBUG view anything that contains 'SECRET, PASSWORD, or PROFANITIES'. This allows untrusted users to be able to give backtraces without seeing sensitive (or offensive) settings.

Still, note that there are always going to be sections of your debug output that are inappropriate for public consumption. File paths, configuration options, and the like all give attackers extra information about your server. Never deploy a site with DEBUG turned on.

DEFAULT_CHARSET

Default: 'utf-8'

This is the default charset to use for all HttpResponse objects, if a MIME type isn't manually specified. It is used with DEFAULT_CONTENT_TYPE to construct the Content-Type header. See Appendix G for more about HttpResponse objects.

DEFAULT_CONTENT_TYPE

Default: 'text/html'

This is the default content type to use for all HttpResponse objects, if a MIME type isn't manually specified. It is used with DEFAULT_CHARSET to construct the Content-Type header. See Appendix G for more about HttpResponse objects.

DEFAULT_FROM_EMAIL

Default: 'webmaster@localhost'

This is the default email address to use for various automated correspondence from the site manager(s).

DISALLOWED_USER_AGENTS

Default: () (empty tuple)

This is a 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 used only if CommonMiddleware is installed (see Chapter 17).

EMAIL_HOST

Default: 'localhost'

This is the host to use for sending email. See also EMAIL_PORT.

EMAIL_HOST_PASSWORD

Default: '' (empty string)

This is the password to use for the SMTP server defined in EMAIL_HOST. This setting is used in conjunction with EMAIL_HOST_USER when authenticating to the SMTP server. If either of these settings is empty, Django won't attempt authentication.

See also EMAIL_HOST_USER.

EMAIL_HOST_USER

Default: '' (empty string)

This is the username to use for the SMTP server defined in EMAIL_HOST. If it's empty, Django won't attempt authentication. See also EMAIL_HOST_PASSWORD.

EMAIL_PORT

Default: 25

This is the port to use for the SMTP server defined in EMAIL_HOST.

EMAIL_SUBJECT_PREFIX

Default: '[Django] '

This is the subject-line prefix for email messages sent with django.core.mail.mail_admins or django.core.mail.mail_managers. You'll probably want to include the trailing space.

FIXTURE_DIRS

Default: () (empty tuple)

This is a list of locations of the fixture data files, in search order. Note that these paths should use Unix-style forward slashes, even on Windows. It is used by Django's testing framework, which is covered online at http://docs.djangoproject.com/en/dev/topics/testing/.

IGNORABLE_404_ENDS

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

This is a tuple of strings that specify beginnings of URLs that should be ignored by the 404 e-mailer. (See Chapter 12 for more on the 404 e-mailer.)

No errors will be sent for URLs end with strings from this sequence.

See also IGNORABLE_404_STARTS and SEND_BROKEN_LINK_EMAILS.

IGNORABLE_404_STARTS

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

See also SEND_BROKEN_LINK_EMAILS and IGNORABLE_404_ENDS.

INSTALLED_APPS

Default: () (empty tuple)

A tuple of strings designating all applications that are enabled in this Django installation. Each string should be a full Python path to a Python package that contains a Django application. See Chapter 5 for more about applications.

LANGUAGE_CODE

Default: 'en-us'

This is a string representing the language code for this installation. This should be in standard language format -- for example, U.S. English is "en-us". See Chapter 19.

LANGUAGES

Default: A tuple of all available languages. This list is continually growing and any copy included here would inevitably become rapidly out of date. You can see the current list of translated languages by looking in django/conf/global_settings.py.

The list is a tuple of two-tuples in the format (language code, language name) -- for example, ('ja', 'Japanese'). This specifies which languages are available for language selection. See Chapter 19 for more on language selection.

Generally, the default value should suffice. Only set this setting if you want to restrict language selection to a subset of the Django-provided languages.

If you define a custom LANGUAGES setting, it's OK to mark the languages as translation strings, but you should never import django.utils.translation from within your settings file, because that module in itself depends on the settings, and that would cause a circular import.

The solution is to use a "dummy" gettext() function. Here's a sample settings file:

gettext = lambda s: s

LANGUAGES = (
    ('de', gettext('German')),
    ('en', gettext('English')),
)

With this arrangement, make-messages.py will still find and mark these strings for translation, but the translation won't happen at runtime -- so you'll have to remember to wrap the languages in the real gettext() in any code that uses LANGUAGES at runtime.

MANAGERS

Default: () (empty tuple)

This tuple is 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)

This is an absolute path to the directory that holds media for this installation (e.g., "/home/media/media.lawrence.com/"). See also MEDIA_URL.

MEDIA_URL

Default: '' (empty string)

This URL handles the media served from MEDIA_ROOT (e.g., "http://media.lawrence.com").

Note that this should have a trailing slash if it has a path component:

See Chapter 12 for more on deployment and serving media.

MIDDLEWARE_CLASSES

Default:

("django.contrib.sessions.middleware.SessionMiddleware",
 "django.contrib.auth.middleware.AuthenticationMiddleware",
 "django.middleware.common.CommonMiddleware",
 "django.middleware.doc.XViewMiddleware")

This is a tuple of middleware classes to use. See Chapter 17.

MONTH_DAY_FORMAT

Default: 'F j'

This is the default formatting to use for date fields on Django admin change-list pages -- and, possibly, by other parts of the system -- in cases when only the month and day are displayed. It accepts the same format as the now tag (see Appendix E, Table E-2).

For example, when a Django admin change-list page is being filtered by a date, the header for a given day displays the day and month. Different locales have different formats. For example, U.S. English would have "January 1," whereas Spanish might have "1 Enero."

See also DATE_FORMAT, DATETIME_FORMAT, TIME_FORMAT, and YEAR_MONTH_FORMAT.

PREPEND_WWW

Default: False

This setting indicates whether to prepend the "www." subdomain to URLs that don't have it. This is used only if CommonMiddleware is installed (see the Chapter 17). See also APPEND_SLASH.

ROOT_URLCONF

Default: Not defined

This is a string representing the full Python import path to your root URLconf (e.g., "mydjangoapps.urls"). See Chapter 3.

SECRET_KEY

Default: (Generated automatically when you start a project)

This is a secret key for this particular Django installation. It is 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 and most of the time you won't need to change it

SEND_BROKEN_LINK_EMAILS

Default: False

This setting indicates whether to send an email to the MANAGERS each time somebody visits a Django-powered page that is 404-ed with a nonempty referer (i.e., a broken link). This is only used if CommonMiddleware is installed (see Chapter 17). See also IGNORABLE_404_STARTS and IGNORABLE_404_ENDS.

SERIALIZATION_MODULES

Default: Not defined.

Serialization is a feature still under heavy development. Refer to the online documentation at http://docs.djangoproject.com/en/dev/topics/serialization/ for more information.

SERVER_EMAIL

Default: 'root@localhost'

This is the email address that error messages come from, such as those sent to ADMINS and MANAGERS.

SESSION_COOKIE_AGE

Default: 1209600 (two weeks, in seconds)

This is the age of session cookies, in seconds. See Chapter 14.

SESSION_COOKIE_DOMAIN

Default: None

This is 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 Chapter 14.

SESSION_COOKIE_NAME

Default: 'sessionid'

This is the name of the cookie to use for sessions; it can be whatever you want. See Chapter 14.

SESSION_COOKIE_SECURE

Default: False

This setting indicates whether to use a secure cookie for the session cookie. If this is set to True, the cookie will be marked as "secure," which means browsers may ensure that the cookie is only sent under an HTTPS connection. See Chapter 14.

SESSION_EXPIRE_AT_BROWSER_CLOSE

Default: False

This setting indicates whether to expire the session when the user closes his browser. See Chapter 14.

SESSION_SAVE_EVERY_REQUEST

Default: False

This setting indicates whether to save the session data on every request. See Chapter 14.

SITE_ID

Default: Not defined

This is the ID, as an integer, of the current site in the django_site database table. It is used so that application data can hook into specific site(s) and a single database can manage content for multiple sites. See Chapter 16.

TEMPLATE_CONTEXT_PROCESSORS

Default:

("django.core.context_processors.auth",
"django.core.context_processors.debug",
"django.core.context_processors.i18n",
"django.core.context_processors.media")

This is a tuple of callables that are used to populate the context in RequestContext. These callables take a request object as their argument and return a dictionary of items to be merged into the context. See Chapter 9.

TEMPLATE_DEBUG

Default: False

This Boolean turns template debug mode on and off. If it is True, the fancy error page will display a detailed report for any TemplateSyntaxError. This report contains the relevant snippet of the template, with the appropriate line highlighted.

Note that Django only displays fancy error pages if DEBUG is True, so you'll want to set that to take advantage of this setting.

See also DEBUG.

TEMPLATE_DIRS

Default: () (empty tuple)

This is a list of locations of the template source files, in search order. Note that these paths should use Unix-style forward slashes, even on Windows. See Chapters 4 and 9.

TEMPLATE_LOADERS

Default:

('django.template.loaders.filesystem.load_template_source',
'django.template.loaders.app_directories.load_template_source')

This is a tuple of callables (as strings) that know how to import templates from various sources. See Chapter 9.

TEMPLATE_STRING_IF_INVALID

Default: '' (Empty string)

This is output, as a string, that the template system should use for invalid (e.g., misspelled) variables. See Chapter 9.

TEST_RUNNER

Default: 'django.test.simple.run_tests'

This is the name of the method to use for starting the test suite. It is used by Django's testing framework, which is covered online at http://docs.djangoproject.com/en/dev/topics/testing/.

TEST_DATABASE_NAME

Default: None

This is the name of database to use when running the test suite. If a value of None is specified, the test database will use the name 'test_' + settings.DATABASE_NAME. See the documentation for Django's testing framework, which is covered online at http://docs.djangoproject.com/en/dev/topics/testing/.

TIME_FORMAT

Default: 'P' (e.g., 4 p.m.)

This is the default formatting to use for time fields on Django admin change-list pages -- and, possibly, by other parts of the system. It accepts the same format as the now tag (see Appendix E, Table E-2).

See also DATE_FORMAT, DATETIME_FORMAT, TIME_FORMAT, YEAR_MONTH_FORMAT, and MONTH_DAY_FORMAT.

TIME_ZONE

Default: 'America/Chicago'

This is a string representing the time zone for this installation. Time zones are in the Unix-standard zic format. One relatively complete list of time zone strings can be found at http://www.postgresql.org/docs/8.1/static/datetime-keywords.html#DATETIME-TIMEZONE-SET-TABLE.

This is the time zone to which Django will convert all dates/times -- not necessarily the time zone of the server. For example, one server may serve multiple Django-powered sites, each with a separate time-zone setting.

Normally, Django sets the os.environ['TZ'] variable to the time zone you specify in the TIME_ZONE setting. Thus, all your views and models will automatically operate in the correct time zone. However, if you're using the manually configuring settings (described above in the section titled "Using Settings Without Setting DJANGO_SETTINGS_MODULE"), Django will not touch the TZ environment variable, and it will be up to you to ensure your processes are running in the correct environment.

Note

Django cannot reliably use alternate time zones in a Windows environment. If you're running Django on Windows, this variable must be set to match the system time zone.

URL_VALIDATOR_USER_AGENT

Default: Django/<version> (http://www.djangoproject.com/)

This is the string to use as the User-Agent header when checking to see if URLs exist (see the verify_exists option on URLField; see Appendix A).

USE_ETAGS

Default: False

This Boolean specifies whether to output the ETag header. It saves bandwidth but slows down performance. This is only used if CommonMiddleware is installed (see Chapter 17).

USE_I18N

Default: True

This Boolean specifies whether Django's internationalization system (see Chapter 19) should be enabled. It provides an easy way to turn off internationalization, for performance. If this is set to False, Django will make some optimizations so as not to load the internationalization machinery.

YEAR_MONTH_FORMAT

Default: 'F Y'

This is the default formatting to use for date fields on Django admin change-list pages -- and, possibly, by other parts of the system -- in cases when only the year and month are displayed. It accepts the same format as the now tag (see Appendix E).

For example, when a Django admin change-list page is being filtered by a date drill-down, the header for a given month displays the month and the year. Different locales have different formats. For example, U.S. English would use "January 2006," whereas another locale might use "2006/January."

See also DATE_FORMAT, DATETIME_FORMAT, TIME_FORMAT, and MONTH_DAY_FORMAT.

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