==========================

Deployment of translations

==========================

If you don't need internationalization

======================================

Django's internationalization hooks are on by default, and that means there's a

bit of i18n-related overhead in certain places of the framework. If you don't

use internationalization, you should take the two seconds to set

:setting:`USE_I18N = False <USE_I18N>` in your settings file. If

:setting:`USE_I18N` is set to ``False``, then Django will make some

optimizations so as not to load the internationalization machinery.

You'll probably also want to remove ``'django.core.context_processors.i18n'``

from your ``TEMPLATE_CONTEXT_PROCESSORS`` setting.

.. note::

    There is also an independent but related :setting:`USE_L10N` setting that

    controls if Django should implement format localization.

    If :setting:`USE_L10N` is set to ``True``, Django will handle numbers times,

    and dates in the format of the current locale. That includes representation

    of these field types on templates and allowed input formats for dates,

    times on model forms.

    See :ref:`format-localization` for more details.

If you do need internationalization

===================================

.. _how-django-discovers-language-preference:

How Django discovers language preference

----------------------------------------

Once you've prepared your translations -- or, if you just want to use the

translations that come with Django -- you'll just need to activate translation

for your app.

Behind the scenes, Django has a very flexible model of deciding which language

should be used -- installation-wide, for a particular user, or both.

To set an installation-wide language preference, set :setting:`LANGUAGE_CODE`.

Django uses this language as the default translation -- the final attempt if no

other translator finds a translation.

If all you want to do is run Django with your native language, and a language

file is available for it, all you need to do is set ``LANGUAGE_CODE``.

If you want to let each individual user specify which language he or she

prefers, use ``LocaleMiddleware``. ``LocaleMiddleware`` enables language

selection based on data from the request. It customizes content for each user.

To use ``LocaleMiddleware``, add ``'django.middleware.locale.LocaleMiddleware'``

to your ``MIDDLEWARE_CLASSES`` setting. Because middleware order matters, you

should follow these guidelines:

    * Make sure it's one of the first middlewares installed.

    * It should come after ``SessionMiddleware``, because ``LocaleMiddleware``

      makes use of session data.

    * If you use ``CacheMiddleware``, put ``LocaleMiddleware`` after it.

For example, your ``MIDDLEWARE_CLASSES`` might look like this::

    MIDDLEWARE_CLASSES = (

       'django.contrib.sessions.middleware.SessionMiddleware',

       'django.middleware.locale.LocaleMiddleware',

       'django.middleware.common.CommonMiddleware',

    )

(For more on middleware, see the :doc:`middleware documentation

</topics/http/middleware>`.)

``LocaleMiddleware`` tries to determine the user's language preference by

following this algorithm:

    * First, it looks for a ``django_language`` key in the current user's

      session.

    * Failing that, it looks for a cookie.

      .. versionchanged:: 1.0

      In Django version 0.96 and before, the cookie's name is hard-coded to

      ``django_language``. In Django 1,0, The cookie name is set by the

      ``LANGUAGE_COOKIE_NAME`` setting. (The default name is

      ``django_language``.)

    * Failing that, it looks at the ``Accept-Language`` HTTP header. This

      header is sent by your browser and tells the server which language(s) you

      prefer, in order by priority. Django tries each language in the header

      until it finds one with available translations.

    * Failing that, it uses the global ``LANGUAGE_CODE`` setting.

.. _locale-middleware-notes:

Notes:

    * In each of these places, the language preference is expected to be in the

      standard :term:`language format<language code>`, as a string. For example,

      Brazilian Portuguese is ``pt-br``.

    * If a base language is available but the sublanguage specified is not,

      Django uses the base language. For example, if a user specifies ``de-at``

      (Austrian German) but Django only has ``de`` available, Django uses

      ``de``.

    * Only languages listed in the :setting:`LANGUAGES` setting can be selected.

      If you want to restrict the language selection to a subset of provided

      languages (because your application doesn't provide all those languages),

      set ``LANGUAGES`` to a list of languages. For example::

          LANGUAGES = (

            ('de', _('German')),

            ('en', _('English')),

          )

      This example restricts languages that are available for automatic

      selection to German and English (and any sublanguage, like de-ch or

      en-us).

    * If you define a custom ``LANGUAGES`` setting, as explained in the

      previous bullet, it's OK to mark the languages as translation strings

      -- but use a "dummy" ``ugettext()`` function, not the one in

      ``django.utils.translation``. 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" ``ugettext()`` function. Here's a sample

      settings file::

          ugettext = lambda s: s

          LANGUAGES = (

              ('de', ugettext('German')),

              ('en', ugettext('English')),

          )

      With this arrangement, ``django-admin.py makemessages`` 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* ``ugettext()`` in any code that uses ``LANGUAGES`` at runtime.

    * The ``LocaleMiddleware`` can only select languages for which there is a

      Django-provided base translation. If you want to provide translations

      for your application that aren't already in the set of translations

      in Django's source tree, you'll want to provide at least a basic

      one as described in the :ref:`Locale restrictions<locale-restrictions>`

      note.

Once ``LocaleMiddleware`` determines the user's preference, it makes this

preference available as ``request.LANGUAGE_CODE`` for each

:class:`~django.http.HttpRequest`. Feel free to read this value in your view

code. Here's a simple example::

    def hello_world(request, count):

        if request.LANGUAGE_CODE == 'de-at':

            return HttpResponse("You prefer to read Austrian German.")

        else:

            return HttpResponse("You prefer to read another language.")

Note that, with static (middleware-less) translation, the language is in

``settings.LANGUAGE_CODE``, while with dynamic (middleware) translation, it's

in ``request.LANGUAGE_CODE``.

.. _settings file: ../settings/

.. _middleware documentation: ../middleware/

.. _session: ../sessions/

.. _request object: ../request_response/#httprequest-objects

How Django discovers translations

---------------------------------

As described in :ref:`using-translations-in-your-own-projects`,

at runtime, Django looks for translations by following this algorithm:

    * First, it looks for a ``locale`` directory in the directory containing

      your settings file.

    * Second, it looks for a ``locale`` directory in the project directory.

    * Third, it looks for a ``locale`` directory in each of the installed apps.

      It does this in the reverse order of INSTALLED_APPS

    * Finally, it checks the Django-provided base translation in

      ``django/conf/locale``.

In all cases the name of the directory containing the translation is expected to

be named using :term:`locale name` notation. E.g. ``de``, ``pt_BR``, ``es_AR``,

etc.