django-parler 1.0b3

Simple Django model translations without nasty hacks, featuring nice admin integration.

django-parler

Simple Django model translations without nasty hacks.

Features:

• Nice admin integration.

• Access translated attributes like regular attributes.

• Automatic fallback to the default language.

• Separate table for translated fields, compatible with django-hvad.

• Plays nice with others, compatible with django-polymorphic, django-mptt and such:

• No ORM query hacks.

• Easy to combine with custom Manager or QuerySet classes.

• Easy to construct the translations model manually when needed.

Installation

First install the module, preferably in a virtual environment:

git clone https://github.com/edoburu/django-parler.git
cd django-parler
pip install .

Configuration

Add the following settings:

INSTALLED_APPS += (
    'parler',
)

By default, the fallback language is the same as LANGUAGE_CODE. The fallback language can be changed in the settings:

PARLER_DEFAULT_LANGUAGE_CODE = 'en'

Optionally, the admin tabs can be configured too:

PARLER_LANGUAGES = {
    None: (
        {'code': 'en',},
        {'code': 'en-us',},
        {'code': 'it',},
        {'code': 'nl',},
    ),
    'default': {
        'fallback': 'en',             # defaults to PARLER_DEFAULT_LANGUAGE_CODE
        'hide_untranslated': False,   # the default; let .active_translations() return fallbacks too.
    }
}

When using settings.SITE_ID which is a setting of the sites framework (django.contrib.sites) the PARLER_LANGUAGES dict can contain site specific settings and the special None key is no longer used:

PARLER_LANGUAGES = {
    # Global site
    1: (
        {'code': 'en',},
        {'code': 'en-us',},
        {'code': 'it',},
        {'code': 'nl',},
    ),
    # US site
    2: (
        {'code': 'en-us',},
        {'code': 'en',},
    ),
    # IT site
    3: (
        {'code': 'it',},
        {'code': 'en',},
    ),
    # NL site
    3: (
        {'code': 'nl',},
        {'code': 'en',},
    ),
    'default': {
        'fallback': 'en',             # defaults to PARLER_DEFAULT_LANGUAGE_CODE
        'hide_untranslated': False,   # the default; let .active_translations() return fallbacks too.
    }
}

Basic example

Extend the model class:

from django.db import models
from parler.models import TranslatableModel, TranslatedFields


class MyModel(TranslatableModel):
    translations = TranslatedFields(
        title = models.CharField(_("Title"), max_length=200)
    )

    class Meta:
        verbose_name = _("MyModel")

    def __unicode__(self):
        return self.title

Now, the title field is translated.

Using translated fields

Translated fields can be accessed directly:

>>> from django.utils import translation
>>> translation.activate('en')

>>> object = MyModel.objects.all()[0]
>>> object.get_current_language()
'en'
>>> object.title
u'cheese omelet'

>>> object.set_current_language('fr')       # Only switches
>>> object.title = "omelette du fromage"    # Translation is created on demand.
>>> object.save()

>>> objects = MyModel.objects.language('fr').all()
>>> objects[0].title
u'omelette du fromage'

When an attribute is not translated yet, the default language (set by PARLER_DEFAULT_LANGUAGE_CODE or PARLER_DEFAULT_LANGUAGE_CODE['default']['fallback']) will be retured.

Querying translated attributes

Currently, this package doesn’t improve the QuerySet API to access translated fields. Hence, simply access the translated fields like any normal relation:

object = MyObject.objects.filter(translations__title='omelette')

translation1 = myobject.translations.all()[0]

Note that due to the Django ORM design, the query for translated attributes should typically occur within a single .filter(..) call. When using .filter(..).filter(..), the ORM turns that into 2 separate joins on the translations table. See the ORM documentation for more details.

Filtering translated objects

To restrict the queryset to translated objects only, the following methods are available:

• MyObject.objects.translated(*language_codes, **translated_fields) - return only objects with a translation of language_codes.

• MyObject.objects.active_translations(language_code=None, **translated_fields) - return only objects for the current language (and fallback if this applies).

The active_translations() method also returns objects which are translated in the fallback language, unless hide_untranslated = True is used in the PARLER_LANGUAGES setting.

Note

These methods perform a query on the translations__language_code field. Hence, they can’t be combined with other filters on translated fields, as that causes double joins on the translations table.

If you have to query a language and translated attribute, query both in a single .filter() call:

from parler.utils import get_active_language_choices

MyObject.objects.filter(
    translations__language_code__in=get_active_language_choices(),
    translations__slug='omelette'
)

For convenience, use the provided methods:

MyObject.objects.translated(get_active_language_choices(), slug='omelette')

MyObject.objects.active_translations(slug='omelette')

Advanced example

The translated model can be constructed manually too:

from django.db import models
from parler.models import TranslatableModel, TranslatedFieldsModel
from parler.fields import TranslatedField


class MyModel(TranslatableModel):
    title = TranslatedField()  # Optional, explicitly mention the field

    class Meta:
        verbose_name = _("MyModel")

    def __unicode__(self):
        return self.title


class MyModel_Translations(TranslatedFieldsModel):
    master = models.ForeignKey(MyModel, related_name='translations', null=True)
    title = models.CharField(_("Title"), max_length=200)

    class Meta:
        verbose_name = _("MyModel translation")

Missing translation fallbacks

When a translation is missing, the fallback language is used. However, when an object only exists in a different language, this still fails.

This package provides 3 solutions to this problem:

1. Declare the translated attribute explicitly with any_language=True:

   class MyModel(TranslatableModel):
       title = TranslatedField(any_language=True)

   Now, the title will try to fetch one of the existing languages from the database.

2. Use model.safe_translation_getter("fieldname", any_language=True) on attributes which don’t have an any_language=True setting.

3. Use a try .. catch TranslationDoesNotExist block for custom handling. Because this exception inherits from AttibuteError, templates typically display empty values by default.

4. Avoid fetching those objects using something like: queryset.active_translations() or queryset.filter(translations__language_code__in=('nl', 'en')).distinct(). Note that the same ORM restrictions apply here.

Background story

This package is inspired by django-hvad. When attempting to integrate multilingual support into django-fluent-pages using django-hvad this turned out to be really hard. The sad truth is that while django-hvad has a nice admin interface, table layout and model API, it also overrides much of the default behavior of querysets and model metaclasses. Currently, this prevents combining django-hvad with django-polymorphic.

When investigating other multilingual packages, they either appeared to be outdated, store translations in the same table (too inflexible for us) or only provided a model API. Hence, there was a need for a new solution, using a simple, crude but effective API.

Initially, multilingual support was coded directly within django-fluent-pages, while keeping a future django-hvad transition in mind. Instead of doing metaclass operations, the “shared model” just proxied all attributes to the translated model (all manually constructed). Queries just had to be performed using .filter(translations__title=..). This proved to be a sane solution and quickly it turned out that this code deserved a separate package, and some other modules needed it too.

This package is an attempt to combine the best of both worlds; the API simplicity of django-hvad with the crude, but effective solution of proxying translated attributes. And yes, we’ve added some metaclass magic too - to make life easier - without loosing the freedom of manually using the API at your will.

TODO

• Documentation on RTD.

• Unittest the admin.

• ModelAdmin.prepopulated_fields doesn’t work yet (you can use get_prepopulated_fields() as workaround).

• The list code currently performs one query per object. This needs to be reduced.

• Preferably, the TranslatedField proxy on the model should behave like a RelatedField, if that would nicely with the ORM too.

Django compatibility

This package has been tested with Django 1.4 and 1.5 on Python 2.6/2.7.

Django 1.4 note

When using Django 1.4, there is a small tweak you’ll have to make in the admin. Instead of using fieldsets = .., use declared_fieldsets = .. on the ModelAdmin definition. The Django 1.4 admin validation doesn’t actualy check the form fields, but only checks whether the fields exist in the model - which they obviously don’t. Using declared_fieldsets instead of fieldsets circumvents this check.

API

On parler.models.TranslatableModel:

• get_current_language()

• set_current_language(language_code, initialize=False)

• get_fallback_language()

• get_available_languages()

• has_translation(language_code=None)

• save_translations()

• safe_translation_getter(field, default=None, any_language=False)

On parler.models.TranslatedFieldsModel:

• language_code - The language code field.

• master - ForeignKey to the shared table.

• is_modified - Property to detect changes.

• get_translated_fields() - The names of translated fields.

On parler.managers.TranslatableManager:

• queryset_class - the attribute that points to the queryset class.

• language(language_code=None) - set the language of returned objects.

• translated(*language_codes) - return only translated objects (NOTE: can’t be combined with other filters)

• active_translations(language_code=None) - return objects of the currently active translation (may include the fallback language too).

On parler.admin.TranslatableAdmin:

• get_form_language(request, obj=None) - return the currently active language in the admin form.

• get_available_languages(obj) - returns the QuerySet with all active languages.

• language_column(obj) - the extra column which can be added to the list_display.

In parler.utils:

• normalize_language_code()

• is_supported_django_language()

• get_language_title()

• get_language_settings()

• get_active_language_choices()

• is_multilingual_project()

Contributing

This module is designed to be generic. In case there is anything you didn’t like about it, or think it’s not flexible enough, please let us know. We’d love to improve it!

If you have any other valuable contribution, suggestion or idea, please let us know as well because we will look into it. Pull requests are welcome too. :-)