FilterSet Options

This document provides a guide on using additional FilterSet features.

Meta options

• model

• fields

• exclude

• form

• filter_overrides

Automatic filter generation with model

The FilterSet is capable of automatically generating filters for a given model’s fields. Similar to Django’s ModelForm, filters are created based on the underlying model field’s type. This option must be combined with either the fields or exclude option, which is the same requirement for Django’s ModelForm class, detailed here.

class UserFilter(django_filters.FilterSet):
    class Meta:
        model = User
        fields = ['username', 'last_login']

Declaring filterable fields

The fields option is combined with model to automatically generate filters. Note that generated filters will not overwrite filters declared on the FilterSet. The fields option accepts two syntaxes:

• a list of field names

• a dictionary of field names mapped to a list of lookups

class UserFilter(django_filters.FilterSet):
    class Meta:
        model = User
        fields = ['username', 'last_login']

# or

class UserFilter(django_filters.FilterSet):
    class Meta:
        model = User
        fields = {
            'username': ['exact', 'contains'],
            'last_login': ['exact', 'year__gt'],
        }

The list syntax will create an exact lookup filter for each field included in fields. The dictionary syntax will create a filter for each lookup expression declared for its corresponding model field. These expressions may include both transforms and lookups, as detailed in the lookup reference.

Note that it is not necessary to include declared filters in a fields list - doing so will only affect the order in which fields appear on a FilterSet’s form. Including declarative aliases in a fields dict will raise an error.

class UserFilter(django_filters.FilterSet):
    username = filters.CharFilter()
    login_timestamp = filters.IsoDateTimeFilter(field_name='last_login')

    class Meta:
        model = User
        fields = {
            'username': ['exact', 'contains'],
            'login_timestamp': ['exact'],
        }

TypeError("'Meta.fields' contains fields that are not defined on this FilterSet: login_timestamp")

Disable filter fields with exclude

The exclude option accepts a blacklist of field names to exclude from automatic filter generation. Note that this option will not disable filters declared directly on the FilterSet.

class UserFilter(django_filters.FilterSet):
    class Meta:
        model = User
        exclude = ['password']

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.

Customise filter generation with filter_overrides

The inner Meta class also takes an optional filter_overrides argument. This is a map of model fields to filter classes with options:

class ProductFilter(django_filters.FilterSet):

     class Meta:
         model = Product
         fields = ['name', 'release_date']
         filter_overrides = {
             models.CharField: {
                 'filter_class': django_filters.CharFilter,
                 'extra': lambda f: {
                     'lookup_expr': 'icontains',
                 },
             },
             models.BooleanField: {
                 'filter_class': django_filters.BooleanFilter,
                 'extra': lambda f: {
                     'widget': forms.CheckboxInput,
                 },
             },
         }

Overriding FilterSet methods

When overriding classmethods, calling super(MyFilterSet, cls) may result in a NameError exception. This is due to the FilterSetMetaclass calling these classmethods before the FilterSet class has been fully created. There are two recommmended workarounds:

1. If using python 3.6 or newer, use the argumentless super() syntax.

2. For older versions of python, use an intermediate class. Ex:

   class Intermediate(django_filters.FilterSet):
   
       @classmethod
       def method(cls, arg):
           super(Intermediate, cls).method(arg)
           ...
   
   class ProductFilter(Intermediate):
       class Meta:
           model = Product
           fields = ['...']
   

filter_for_lookup()

Prior to version 0.13.0, filter generation did not take into account the lookup_expr used. This commonly caused malformed filters to be generated for ‘isnull’, ‘in’, and ‘range’ lookups (as well as transformed lookups). The current implementation provides the following behavior:

• ‘isnull’ lookups return a BooleanFilter

• ‘in’ lookups return a filter derived from the CSV-based BaseInFilter.

• ‘range’ lookups return a filter derived from the CSV-based BaseRangeFilter.

If you want to override the filter_class and params used to instantiate filters for a model field, you can override filter_for_lookup(). Ex:

class ProductFilter(django_filters.FilterSet):
    class Meta:
        model = Product
        fields = {
            'release_date': ['exact', 'range'],
        }

    @classmethod
    def filter_for_lookup(cls, f, lookup_type):
        # override date range lookups
        if isinstance(f, models.DateField) and lookup_type == 'range':
            return django_filters.DateRangeFilter, {}

        # use default behavior otherwise
        return super().filter_for_lookup(f, lookup_type)