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 USE_I18N = False in your settings file. If 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 USE_L10N setting that controls if Django should implement format localization.
If 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 Format localization for more details.
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 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:
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 middleware documentation.)
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.
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.
Notes:
In each of these places, the language preference is expected to be in the standard language format, 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 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 Locale restrictions note.
Once LocaleMiddleware determines the user's preference, it makes this preference available as request.LANGUAGE_CODE for each 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.
As described in Using internationalization in your own projects, at runtime, Django looks for translations by following this algorithm:
In all cases the name of the directory containing the translation is expected to be named using locale name notation. E.g. de, pt_BR, es_AR, etc.
Jul 05, 2010