Using django-filter =================== Django-filter provides a simple way to filter down a queryset based on parameters a user provides. Say we have a ``Product`` model and we want to let our users filter which products they see on a list page. The model --------- Let's start with our model:: from django.db import models class Product(models.Model): name = models.CharField(max_length=255) price = models.DecimalField() description = models.TextField() release_date = models.DateField() manufacturer = models.ForeignKey(Manufacturer) The filter ---------- We have a number of fields and we want to let our users filter based on the price or the release_date. We create a ``FilterSet`` for this:: import django_filters class ProductFilter(django_filters.FilterSet): class Meta: model = Product fields = ['price', 'release_date'] As you can see this uses a very similar API to Django's ``ModelForm``. Just like with a ``ModelForm`` we can also override filters, or add new ones using a declarative syntax:: import django_filters class ProductFilter(django_filters.FilterSet): price = django_filters.NumberFilter(lookup_type='lt') class Meta: model = Product fields = ['price', 'release_date'] Filters take a ``lookup_type`` argument which specifies what lookup type to use with `Django's ORM`_. So here when a user entered a price it would show all Products with a price less than that. .. _`Django's ORM`: https://docs.djangoproject.com/en/dev/ref/models/querysets/#field-lookups **It's quite common to forget to set lookup type for `CharField`s/`TextField`s and wonder why search for "foo" doesn't return result for "foobar". It's because default lookup type is exact text, but you probably want `icontains` lookup field.** The FilterSet Meta class fields can additionally be set using a Dictionary to specify multiple ``lookup_type`` filters without significant code duplication:: import django_filters class ProductFilter(django_filters.FilterSet): class Meta: model = Product fields = {'price': ['lt', 'gt'], 'release_date': ['exact'], } The above would generate 'price__lt', 'price__gt' and 'release_date' filters. The filter lookup type keyword 'exact' is the default and therefore never added to a filter name. Items in the ``fields`` sequence in the ``Meta`` class may include "relationship paths" using Django's ``__`` syntax to filter on fields on a related model:: class ProductFilter(django_filters.FilterSet): class Meta: model = Product fields = ['manufacturer__country'] Filters also take any arbitrary keyword arguments which get passed onto the ``django.forms.Field`` initializer. These extra keyword arguments get stored in ``Filter.extra``, so it's possible to override the initializer of a ``FilterSet`` to add extra ones:: class ProductFilter(django_filters.FilterSet): class Meta: model = Product fields = ['manufacturer'] def __init__(self, *args, **kwargs): super(ProductFilter, self).__init__(*args, **kwargs) self.filters['manufacturer'].extra.update( {'empty_label': 'All Manufacturers'}) Like ``django.contrib.admin.ModelAdmin``, it is possible to override default filters for all the models fields of the same kind using ``filter_overrides``:: class ProductFilter(django_filters.FilterSet): filter_overrides = { models.CharField: { 'filter_class': django_filters.CharFilter, 'extra': lambda f: { 'lookup_type': 'icontains', } } } class Meta: model = Product fields = ['name'] MethodFilter ~~~~~~~~~~~~~~~~~~~~~~~~~~~ If you want fine control over each individual filter attribute, you can use the ``MethodFilter`` filter. By passing in the name of a custom defined filter function as an ``action``, the filter attribute gets linked to the custom filter function. Here is an example of overriding the filter function of the filter attribute ``username`` :: class F(django_filters.FilterSet): username = MethodFilter(action='my_custom_filter') class Meta: model = User fields = ['username'] def my_custom_filter(self, queryset, value): return queryset.filter( username=value ) The filter function can also be defined outside of the filter class scope. Though you would need to pass in the actual function value, not it's name. :: def my_custom_filter(queryset, value): return queryset.filter( username=value ) class F(django_filters.FilterSet): # Notice: In this case, action accepts a func, not a string username = MethodFilter(action=filter_username) class Meta: model = User fields = ['username'] Lastly, when using a ``MethodFilter``, there is no need to define an action. You may simply do the following and ``filter_username`` will be auto-detected and used. :: class F(FilterSet): username = MethodFilter() class Meta: model = User fields = ['username'] def filter_username(self, queryset, value): return queryset.filter( username__contains='ke' ) Under the hood, if ``action`` not is defined, ``django_filter`` searches for a class method with a name that follows the pattern ``filter_{{ATTRIBUTE_NAME}}``. For example, if the attribute name is ``email``, then the filter class will be scanned for the filter function ``filter_email``. If no action is provided, and no filter class function is found, then the filter attribute will be left unfiltered. The view -------- Now we need to write a view:: def product_list(request): f = ProductFilter(request.GET, queryset=Product.objects.all()) return render_to_response('my_app/template.html', {'filter': f}) If a queryset argument isn't provided then all the items in the default manager of the model will be used. If you want to access the filtered objects in your views, for example if you want to paginate them, you can do that. They are in f.qs The URL conf ------------ We need a URL pattern to call the view:: url(r'^list$', views.product_list) The template ------------ And lastly we need a template:: {% extends "base.html" %} {% block content %} <form action="" method="get"> {{ filter.form.as_p }} <input type="submit" /> </form> {% for obj in filter %} {{ obj.name }} - ${{ obj.price }}<br /> {% endfor %} {% endblock %} And that's all there is to it! The ``form`` attribute contains a normal Django form, and when we iterate over the ``FilterSet`` we get the objects in the resulting queryset. Other Meta options ------------------ Ordering using ``order_by`` ~~~~~~~~~~~~~~~~~~~~~~~~~~~ You can allow the user to control ordering by providing the ``order_by`` argument in the Filter's Meta class. ``order_by`` can be either a ``list`` or ``tuple`` of field names, in which case those are the options, or it can be a ``bool`` which, if True, indicates that all fields that the user can filter on can also be sorted on. An example or ordering using a list:: import django_filters class ProductFilter(django_filters.FilterSet): price = django_filters.NumberFilter(lookup_type='lt') class Meta: model = Product fields = ['price', 'release_date'] order_by = ['price'] If you want to control the display of items in ``order_by``, you can set it to a list or tuple of 2-tuples in the format ``(field_name, display_name)``. This lets you override the displayed names for your ordering fields:: order_by = ( ('name', 'Company Name'), ('average_rating', 'Stars'), ) Note that the default query parameter name used for ordering is ``o``. You can override this by setting an ``order_by_field`` attribute on the ``FilterSet`` class to the string value you would like to use. Custom Forms using ``form`` ~~~~~~~~~~~~~~~~~~~~~~~~~~~ The inner ``Meta`` class also takes an optional ``form`` argument. This is a form class from which ``FilterSet.form`` will subclass. This works similar to the ``form`` option on a ``ModelAdmin.`` Group fields with ``together`` ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ The inner ``Meta`` class also takes an optional ``together`` argument. This is a list of lists, each containing field names. For convenience can be a single list/tuple when dealing with a single set of fields. Fields within a field set must either be all or none present in the request for ``FilterSet.form`` to be valid:: import django_filters class ProductFilter(django_filters.FilterSet): class Meta: model = Product fields = ['price', 'release_date', 'rating'] together = ['rating', 'price'] Non-Meta options ---------------- Note that these options do not go in the Meta class, they are specified directly in your FilterSet class. ``strict`` ~~~~~~~~~~ The ``strict`` option controls whether results are returned when an invalid value is specified by the user for any filter field. By default, ``strict`` is set to ``STRICTNESS.RETURN_NO_RESULTS`` meaning that an empty queryset is returned if any field contains an invalid value. You can loosen this behavior by setting ``strict`` to ``STRICTNESS.IGNORE`` which will effectively ignore a filter field if its value is invalid. A third option of ``STRICTNESS.RAISE_VALIDATION_ERROR`` will cause a ``ValidationError` to be raised if any field contains an invalid value. Overriding ``FilterSet`` methods -------------------------------- ``get_ordering_field()`` ~~~~~~~~~~~~~~~~~~~~~~~~ If you want to use a custom widget, or in any other way override the ordering field you can override the ``get_ordering_field()`` method on a ``FilterSet``. This method just needs to return a Form Field. Ordering on multiple fields, or other complex orderings can be achieved by overriding the ``FilterSet.get_order_by()`` method. This is passed the selected ``order_by`` value, and is expected to return an iterable of values to pass to ``QuerySet.order_by``. For example, to sort a ``User`` table by last name, then first name:: class UserFilter(django_filters.FilterSet): class Meta: order_by = ( ('username', 'Username'), ('last_name', 'Last Name') ) def get_order_by(self, order_value): if order_value == 'last_name': return ['last_name', 'first_name'] return super(UserFilter, self).get_order_by(order_value) Generic View ------------ In addition to the above usage there is also a class-based generic view included in django-filter, which lives at ``django_filters.views.FilterView``. You must provide either a ``model`` or ``filterset_class`` argument, similar to ``ListView`` in Django itself:: # urls.py from django.conf.urls import patterns, url from django_filters.views import FilterView from myapp.models import Product urlpatterns = patterns('', (r'^list/$', FilterView.as_view(model=Product)), ) You must provide a template at ``<app>/<model>_filter.html`` which gets the context parameter ``filter``. Additionally, the context will contain ``object_list`` which holds the filtered queryset. A legacy functional generic view is still included in django-filter, although its use is deprecated. It can be found at ``django_filters.views.object_filter``. You must provide the same arguments to it as the class based view:: # urls.py from django.conf.urls import patterns, url from myapp.models import Product urlpatterns = patterns('', (r'^list/$', 'django_filters.views.object_filter', {'model': Product}), ) The needed template and its context variables will also be the same as the class-based view above.