[1.1.X] Fixed #10260 - Refactored internationalization documentation. Thanks, Ramiro Morales.

.. _howto-i18n:

.. _using-translations-in-your-own-projects:

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

Using internationalization in your own projects

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

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

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

      of the view that's being called. If it finds a translation for the

      selected language, the translation will be installed.

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

      finds a translation, the translation will be installed.

    * 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.

This way, you can write applications that include their own translations, and

you can override base translations in your project path. Or, you can just build

a big project out of several apps and put all translations into one big project

message file. The choice is yours.

.. note::

    If you're using manually configured settings, as described in

    :ref:`settings-without-django-settings-module`, the ``locale`` directory in

    the project directory will not be examined, since Django loses the ability

    to work out the location of the project directory. (Django normally uses the

    location of the settings file to determine this, and a settings file doesn't

    exist if you're manually configuring your settings.)

All message file repositories are structured the same way. They are:

    * ``$APPPATH/locale/<language>/LC_MESSAGES/django.(po|mo)``

    * ``$PROJECTPATH/locale/<language>/LC_MESSAGES/django.(po|mo)``

    * All paths listed in ``LOCALE_PATHS`` in your settings file are

      searched in that order for ``<language>/LC_MESSAGES/django.(po|mo)``

    * ``$PYTHONPATH/django/conf/locale/<language>/LC_MESSAGES/django.(po|mo)``

To create message files, you use the :djadmin:`django-admin.py makemessages <makemessages>`

tool. You only need to be in the same directory where the ``locale/`` directory

is located. And you use :djadmin:`django-admin.py compilemessages <compilemessages>`

to produce the binary ``.mo`` files that are used by ``gettext``. Read the

:ref:`topics-i18n-localization` document for more details.

You can also run ``django-admin.py compilemessages --settings=path.to.settings``

to make the compiler process all the directories in your :setting:`LOCALE_PATHS`

setting.

Application message files are a bit complicated to discover -- they need the

:class:`~django.middleware.locale.LocaleMiddleware`. If you don't use the

middleware, only the Django message files and project message files will be

installed and available at runtime.

Finally, you should give some thought to the structure of your translation

files. If your applications need to be delivered to other users and will

be used in other projects, you might want to use app-specific translations.

But using app-specific translations and project translations could produce

weird problems with ``makemessages``: It will traverse all directories below

the current path and so might put message IDs into the project message file

that are already in application message files.

The easiest way out is to store applications that are not part of the project

(and so carry their own translations) outside the project tree. That way,

``django-admin.py makemessages`` on the project level will only translate

strings that are connected to your explicit project and not strings that are

distributed independently.

   deployment/index

   error-reporting

   initial-data

   i18n

   jython

   legacy-databases

   outputting-csv

    * Join the `Django i18n mailing list`_ and introduce yourself.

    * Make sure you read the notes about :ref:`specialties-of-django-i18n`.

    * Create translations using the methods described in the

      :ref:`i18n documentation <topics-i18n>`. For this you will use the

      ``django-admin.py makemessages`` tool. In this particular case it should

      be run from the top-level ``django`` directory of the Django source tree.

      :ref:`localization documentation <topics-i18n-localization>`. For this

      you will use the ``django-admin.py makemessages`` tool. In this

      particular case it should be run from the top-level ``django`` directory

      of the Django source tree.

      The script runs over the entire Django source tree and pulls out all

      strings marked for translation. It creates (or updates) a message file in

      the directory ``conf/locale`` (for example for ``pt-BR``, the file will be

      ``conf/locale/pt-br/LC_MESSAGES/django.po``).

      the directory ``conf/locale`` (for example for ``pt_BR``, the file will be

      ``conf/locale/pt_BR/LC_MESSAGES/django.po``).

    * Make sure that ``django-admin.py compilemessages -l <lang>`` runs without

      producing any warnings.

      ``-d djangojs`` command line option to the ``django-admin.py``

      invocations).

    * Create a diff of the ``.po`` file(s) against the current Subversion trunk.

    * Create a diff against the current Subversion trunk.

    * Open a ticket in Django's ticket system, set its ``Component`` field to

      ``Translations``, and attach the patch to it.

Default: ``'en-us'``

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

:ref:`topics-i18n`.

standard :term:`language format<language code>`. For example, U.S. English is

``"en-us"``. See :ref:`topics-i18n`.

.. setting:: LANGUAGE_COOKIE_NAME

.. _online source: http://code.djangoproject.com/browser/django/trunk/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 :ref:`topics-i18n`.

The list is a tuple of two-tuples in the format ``(language code, language

name)``, the ``language code`` part should be a

:term:`language name<language code>` -- for example, ``('ja', 'Japanese')``.

This specifies which languages are available for language selection. See

:ref:`topics-i18n`.

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.

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

A tuple of directories where Django looks for translation files.

See :ref:`translations-in-your-own-projects`.

See :ref:`using-translations-in-your-own-projects`.

.. setting:: LOGIN_REDIRECT_URL

.. _topics-i18n-deployment:

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

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.

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 :ref:`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).

      .. _LANGUAGES setting: ../settings/#languages

    * 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 application directory

      of the view that's being called. If it finds a translation for the

      selected language, the translation will be installed.

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

      finds a translation, the translation will be installed.

    * 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.