Django documentation

  • 1.3
  • Documentation version: 1.2



The goal of internationalization is to allow a single Web application to offer its content and functionality in multiple languages and locales.

For text translations, you, the Django developer, can accomplish this goal by adding a minimal amount of hooks to your Python and templates. These hooks are called translation strings. They tell Django: “This text should be translated into the end user’s language, if a translation for this text is available in that language.” It’s your responsibility to mark translatable strings; the system can only translate strings it knows about.

Django takes care of using these hooks to translate Web apps, on the fly, according to users’ language preferences.

Specifying translation strings: In Python code

Standard translation

Specify a translation string by using the function ugettext(). It’s convention to import this as a shorter alias, _, to save typing.


Python’s standard library gettext module installs _() into the global namespace, as an alias for gettext(). In Django, we have chosen not to follow this practice, for a couple of reasons:

  1. For international character set (Unicode) support, ugettext() is more useful than gettext(). Sometimes, you should be using ugettext_lazy() as the default translation method for a particular file. Without _() in the global namespace, the developer has to think about which is the most appropriate translation function.
  2. The underscore character (_) is used to represent “the previous result” in Python’s interactive shell and doctest tests. Installing a global _() function causes interference. Explicitly importing ugettext() as _() avoids this problem.

In this example, the text "Welcome to my site." is marked as a translation string:

from django.utils.translation import ugettext as _

def my_view(request):
    output = _("Welcome to my site.")
    return HttpResponse(output)

Obviously, you could code this without using the alias. This example is identical to the previous one:

from django.utils.translation import ugettext

def my_view(request):
    output = ugettext("Welcome to my site.")
    return HttpResponse(output)

Translation works on computed values. This example is identical to the previous two:

def my_view(request):
    words = ['Welcome', 'to', 'my', 'site.']
    output = _(' '.join(words))
    return HttpResponse(output)

Translation works on variables. Again, here's an identical example:

def my_view(request):
    sentence = 'Welcome to my site.'
    output = _(sentence)
    return HttpResponse(output)

(The caveat with using variables or computed values, as in the previous two examples, is that Django's translation-string-detecting utility, makemessages, won't be able to find these strings. More on makemessages later.)

The strings you pass to _() or ugettext() can take placeholders, specified with Python's standard named-string interpolation syntax. Example:

def my_view(request, m, d):
    output = _('Today is %(month)s %(day)s.') % {'month': m, 'day': d}
    return HttpResponse(output)

This technique lets language-specific translations reorder the placeholder text. For example, an English translation may be "Today is November 26.", while a Spanish translation may be "Hoy es 26 de Noviembre." -- with the the month and the day placeholders swapped.

For this reason, you should use named-string interpolation (e.g., %(day)s) instead of positional interpolation (e.g., %s or %d) whenever you have more than a single parameter. If you used positional interpolation, translations wouldn't be able to reorder placeholder text.

Marking strings as no-op

Use the function django.utils.translation.ugettext_noop() to mark a string as a translation string without translating it. The string is later translated from a variable.

Use this if you have constant strings that should be stored in the source language because they are exchanged over systems or users -- such as strings in a database -- but should be translated at the last possible point in time, such as when the string is presented to the user.


Use the function django.utils.translation.ungettext() to specify pluralized messages.

ungettext takes three arguments: the singular translation string, the plural translation string and the number of objects.

This function is useful when you need your Django application to be localizable to languages where the number and complexity of plural forms is greater than the two forms used in English ('object' for the singular and 'objects' for all the cases where count is different from zero, irrespective of its value.)

For example:

from django.utils.translation import ungettext
def hello_world(request, count):
    page = ungettext('there is %(count)d object', 'there are %(count)d objects', count) % {
        'count': count,
    return HttpResponse(page)

In this example the number of objects is passed to the translation languages as the count variable.

Lets see a slightly more complex usage example:

from django.utils.translation import ungettext

count = Report.objects.count()
if count == 1:
    name = Report._meta.verbose_name
    name = Report._meta.verbose_name_plural

text = ungettext(
        'There is %(count)d %(name)s available.',
        'There are %(count)d %(name)s available.',
) % {
    'count': count,
    'name': name

Here we reuse localizable, hopefully already translated literals (contained in the verbose_name and verbose_name_plural model Meta options) for other parts of the sentence so all of it is consistently based on the cardinality of the elements at play.


When using this technique, make sure you use a single name for every extrapolated variable included in the literal. In the example above note how we used the name Python variable in both translation strings. This example would fail:

from django.utils.translation import ungettext
from myapp.models import Report

count = Report.objects.count()
d = {
    'count': count,
    'name': Report._meta.verbose_name,
    'plural_name': Report._meta.verbose_name_plural
text = ungettext(
        'There is %(count)d %(name)s available.',
        'There are %(count)d %(plural_name)s available.',
) % d

You would get a a format specification for argument 'name', as in 'msgstr[0]', doesn't exist in 'msgid' error when running compilemessages.

Lazy translation

Use the function django.utils.translation.ugettext_lazy() to translate strings lazily -- when the value is accessed rather than when the ugettext_lazy() function is called.

For example, to translate a model's help_text, do the following:

from django.utils.translation import ugettext_lazy

class MyThing(models.Model):
    name = models.CharField(help_text=ugettext_lazy('This is the help text'))

In this example, ugettext_lazy() stores a lazy reference to the string -- not the actual translation. The translation itself will be done when the string is used in a string context, such as template rendering on the Django admin site.

The result of a ugettext_lazy() call can be used wherever you would use a unicode string (an object with type unicode) in Python. If you try to use it where a bytestring (a str object) is expected, things will not work as expected, since a ugettext_lazy() object doesn't know how to convert itself to a bytestring. You can't use a unicode string inside a bytestring, either, so this is consistent with normal Python behavior. For example:

# This is fine: putting a unicode proxy into a unicode string.
u"Hello %s" % ugettext_lazy("people")

# This will not work, since you cannot insert a unicode object
# into a bytestring (nor can you insert our unicode proxy there)
"Hello %s" % ugettext_lazy("people")

If you ever see output that looks like "hello <django.utils.functional...>", you have tried to insert the result of ugettext_lazy() into a bytestring. That's a bug in your code.

If you don't like the verbose name ugettext_lazy, you can just alias it as _ (underscore), like so:

from django.utils.translation import ugettext_lazy as _

class MyThing(models.Model):
    name = models.CharField(help_text=_('This is the help text'))

Always use lazy translations in Django models. Field names and table names should be marked for translation (otherwise, they won't be translated in the admin interface). This means writing explicit verbose_name and verbose_name_plural options in the Meta class, though, rather than relying on Django's default determination of verbose_name and verbose_name_plural by looking at the model's class name:

from django.utils.translation import ugettext_lazy as _

class MyThing(models.Model):
    name = models.CharField(_('name'), help_text=_('This is the help text'))
    class Meta:
        verbose_name = _('my thing')
        verbose_name_plural = _('mythings')

Notes on model classes translation

Your model classes may not only contain normal fields: you may have relations (with a ForeignKey field) or additional model methods you may use for columns in the Django admin site.

If you have models with foreign keys and you use the Django admin site, you can provide translations for the relation itself by using the verbose_name parameter on the ForeignKey object:

class MyThing(models.Model):
    kind = models.ForeignKey(ThingKind, related_name='kinds',

As you would do for the verbose_name and verbose_name_plural settings of a model Meta class, you should provide a lowercase verbose name text for the relation as Django will automatically titlecase it when required.

For model methods, you can provide translations to Django and the admin site with the short_description parameter set on the corresponding method:

class MyThing(models.Model):
    kind = models.ForeignKey(ThingKind, related_name='kinds',

    def is_mouse(self):
        return self.kind.type == MOUSE_TYPE
    is_mouse.short_description = _('Is it a mouse?')

As always with model classes translations, don't forget to use the lazy translation method!

Working with lazy translation objects

Using ugettext_lazy() and ungettext_lazy() to mark strings in models and utility functions is a common operation. When you're working with these objects elsewhere in your code, you should ensure that you don't accidentally convert them to strings, because they should be converted as late as possible (so that the correct locale is in effect). This necessitates the use of a couple of helper functions.

Joining strings: string_concat()

Standard Python string joins (''.join([...])) will not work on lists containing lazy translation objects. Instead, you can use django.utils.translation.string_concat(), which creates a lazy object that concatenates its contents and converts them to strings only when the result is included in a string. For example:

from django.utils.translation import string_concat
name = ugettext_lazy(u'John Lennon')
instrument = ugettext_lazy(u'guitar')
result = string_concat(name, ': ', instrument)

In this case, the lazy translations in result will only be converted to strings when result itself is used in a string (usually at template rendering time).

The allow_lazy() decorator

Django offers many utility functions (particularly in django.utils) that take a string as their first argument and do something to that string. These functions are used by template filters as well as directly in other code.

If you write your own similar functions and deal with translations, you'll face the problem of what to do when the first argument is a lazy translation object. You don't want to convert it to a string immediately, because you might be using this function outside of a view (and hence the current thread's locale setting will not be correct).

For cases like this, use the django.utils.functional.allow_lazy() decorator. It modifies the function so that if it's called with a lazy translation as the first argument, the function evaluation is delayed until it needs to be converted to a string.

For example:

from django.utils.functional import allow_lazy

def fancy_utility_function(s, ...):
    # Do some conversion on string 's'
fancy_utility_function = allow_lazy(fancy_utility_function, unicode)

The allow_lazy() decorator takes, in addition to the function to decorate, a number of extra arguments (*args) specifying the type(s) that the original function can return. Usually, it's enough to include unicode here and ensure that your function returns only Unicode strings.

Using this decorator means you can write your function and assume that the input is a proper string, then add support for lazy translation objects at the end.

Specifying translation strings: In template code

Translations in Django templates uses two template tags and a slightly different syntax than in Python code. To give your template access to these tags, put {% load i18n %} toward the top of your template.

trans template tag

The {% trans %} template tag translates either a constant string (enclosed in single or double quotes) or variable content:

<title>{% trans "This is the title." %}</title>
<title>{% trans myvar %}</title>

If the noop option is present, variable lookup still takes place but the translation is skipped. This is useful when "stubbing out" content that will require translation in the future:

<title>{% trans "myvar" noop %}</title>

Internally, inline translations use an ugettext call.

In case a template var (myvar above) is passed to the tag, the tag will first resolve such variable to a string at run-time and then look up that string in the message catalogs.

It's not possible to mix a template variable inside a string within {% trans %}. If your translations require strings with variables (placeholders), use {% blocktrans %} instead.

blocktrans template tag

Contrarily to the trans tag, the blocktrans tag allows you to mark complex sentences consisting of literals and variable content for translation by making use of placeholders:

{% blocktrans %}This string will have {{ value }} inside.{% endblocktrans %}

To translate a template expression -- say, accessing object attributes or using template filters -- you need to bind the expression to a local variable for use within the translation block. Examples:

{% blocktrans with article.price as amount %}
That will cost $ {{ amount }}.
{% endblocktrans %}

{% blocktrans with value|filter as myvar %}
This will have {{ myvar }} inside.
{% endblocktrans %}

If you need to bind more than one expression inside a blocktrans tag, separate the pieces with and:

{% blocktrans with book|title as book_t and author|title as author_t %}
This is {{ book_t }} by {{ author_t }}
{% endblocktrans %}

This tag also provides for pluralization. To use it:

  • Designate and bind a counter value with the name count. This value will be the one used to select the right plural form.
  • Specify both the singular and plural forms separating them with the {% plural %} tag within the {% blocktrans %} and {% endblocktrans %} tags.

An example:

{% blocktrans count list|length as counter %}
There is only one {{ name }} object.
{% plural %}
There are {{ counter }} {{ name }} objects.
{% endblocktrans %}

A more complex example:

{% blocktrans with article.price as amount count i.length as years %}
That will cost $ {{ amount }} per year.
{% plural %}
That will cost $ {{ amount }} per {{ years }} years.
{% endblocktrans %}

When you use both the pluralization feature and bind values to local variables in addition to the counter value, keep in mind that the blocktrans construct is internally converted to an ungettext call. This means the same notes regarding ungettext variables apply.

Reverse URL lookups cannot be carried out within the blocktrans and should be retrieved (and stored) beforehand:

{% url arg arg2 as the_url %}
{% blocktrans %}
This is a URL: {{ the_url }}
{% endblocktrans %}

Other tags

Each RequestContext has access to three translation-specific variables:

  • LANGUAGES is a list of tuples in which the first element is the language code and the second is the language name (translated into the currently active locale).
  • LANGUAGE_CODE is the current user's preferred language, as a string. Example: en-us. (See How Django discovers language preference.)
  • LANGUAGE_BIDI is the current locale's direction. If True, it's a right-to-left language, e.g.: Hebrew, Arabic. If False it's a left-to-right language, e.g.: English, French, German etc.

If you don't use the RequestContext extension, you can get those values with three tags:

{% get_current_language as LANGUAGE_CODE %}
{% get_available_languages as LANGUAGES %}
{% get_current_language_bidi as LANGUAGE_BIDI %}

These tags also require a {% load i18n %}.

Translation hooks are also available within any template block tag that accepts constant strings. In those cases, just use _() syntax to specify a translation string:

{% some_special_tag _("Page not found") value|yesno:_("yes,no") %}

In this case, both the tag and the filter will see the already-translated string, so they don't need to be aware of translations.


In this example, the translation infrastructure will be passed the string "yes,no", not the individual strings "yes" and "no". The translated string will need to contain the comma so that the filter parsing code knows how to split up the arguments. For example, a German translator might translate the string "yes,no" as "ja,nein" (keeping the comma intact).

Specifying translation strings: In JavaScript code

Adding translations to JavaScript poses some problems:

  • JavaScript code doesn't have access to a gettext implementation.
  • JavaScript code doesn't have access to .po or .mo files; they need to be delivered by the server.
  • The translation catalogs for JavaScript should be kept as small as possible.

Django provides an integrated solution for these problems: It passes the translations into JavaScript, so you can call gettext, etc., from within JavaScript.

The javascript_catalog view


The main solution to these problems is the django.views.i18n.javascript_catalog() view, which sends out a JavaScript code library with functions that mimic the gettext interface, plus an array of translation strings. Those translation strings are taken from the application, project or Django core, according to what you specify in either the info_dict or the URL.

You hook it up like this:

js_info_dict = {
    'packages': ('',),

urlpatterns = patterns('',
    (r'^jsi18n/$', 'django.views.i18n.javascript_catalog', js_info_dict),

Each string in packages should be in Python dotted-package syntax (the same format as the strings in INSTALLED_APPS) and should refer to a package that contains a locale directory. If you specify multiple packages, all those catalogs are merged into one catalog. This is useful if you have JavaScript that uses strings from different applications.

By default, the view uses the djangojs gettext domain. This can be changed by altering the domain argument.

You can make the view dynamic by putting the packages into the URL pattern:

urlpatterns = patterns('',
    (r'^jsi18n/(?P<packages>\S+?)/$', 'django.views.i18n.javascript_catalog'),

With this, you specify the packages as a list of package names delimited by '+' signs in the URL. This is especially useful if your pages use code from different apps and this changes often and you don't want to pull in one big catalog file. As a security measure, these values can only be either django.conf or any package from the INSTALLED_APPS setting.

Using the JavaScript translation catalog

To use the catalog, just pull in the dynamically generated script like this:

<script type="text/javascript" src="{% url django.views.i18n.javascript_catalog %}"></script>

This uses reverse URL lookup to find the URL of the JavaScript catalog view. When the catalog is loaded, your JavaScript code can use the standard gettext interface to access it:

document.write(gettext('this is to be translated'));

There is also an ngettext interface:

var object_cnt = 1 // or 0, or 2, or 3, ...
s = ngettext('literal for the singular case',
        'literal for the plural case', object_cnt);

and even a string interpolation function:

function interpolate(fmt, obj, named);

The interpolation syntax is borrowed from Python, so the interpolate function supports both positional and named interpolation:

  • Positional interpolation: obj contains a JavaScript Array object whose elements values are then sequentially interpolated in their corresponding fmt placeholders in the same order they appear. For example:

    fmts = ngettext('There is %s object. Remaining: %s',
            'There are %s objects. Remaining: %s', 11);
    s = interpolate(fmts, [11, 20]);
    // s is 'There are 11 objects. Remaining: 20'
  • Named interpolation: This mode is selected by passing the optional boolean named parameter as true. obj contains a JavaScript object or associative array. For example:

    d = {
        count: 10,
        total: 50
    fmts = ngettext('Total: %(total)s, there is %(count)s object',
    'there are %(count)s of a total of %(total)s objects', d.count);
    s = interpolate(fmts, d, true);

You shouldn't go over the top with string interpolation, though: this is still JavaScript, so the code has to make repeated regular-expression substitutions. This isn't as fast as string interpolation in Python, so keep it to those cases where you really need it (for example, in conjunction with ngettext to produce proper pluralizations).

The set_language redirect view


As a convenience, Django comes with a view, django.views.i18n.set_language(), that sets a user's language preference and redirects back to the previous page.

Activate this view by adding the following line to your URLconf:

(r'^i18n/', include('django.conf.urls.i18n')),

(Note that this example makes the view available at /i18n/setlang/.)

The view expects to be called via the POST method, with a language parameter set in request. If session support is enabled, the view saves the language choice in the user's session. Otherwise, it saves the language choice in a cookie that is by default named django_language. (The name can be changed through the LANGUAGE_COOKIE_NAME setting.)

After setting the language choice, Django redirects the user, following this algorithm:

  • Django looks for a next parameter in the POST data.
  • If that doesn't exist, or is empty, Django tries the URL in the Referrer header.
  • If that's empty -- say, if a user's browser suppresses that header -- then the user will be redirected to / (the site root) as a fallback.

Here's example HTML template code:

<form action="/i18n/setlang/" method="post">
{% csrf_token %}
<input name="next" type="hidden" value="/next/page/" />
<select name="language">
{% for lang in LANGUAGES %}
<option value="{{ lang.0 }}">{{ lang.1 }}</option>
{% endfor %}
<input type="submit" value="Go" />


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