How to override the queryset giving the filters in list_filter?

Question

Given the following models

class AnotherModel(models.Model):     n = models.IntegerField()  class MyModel(models.Model):     somefield = models.ForeignKey(AnotherModel) 

and admin

class MyModelAdmin(admin.ModelAdmin):             list_filter = ('somefield',) 

how can I filter the instances of AnotherModel to show only those with a given n value in my admin filter?

I need something like:

Filter

By somefield

all

[list of AnotherModel instances with given n]

Answer 1

See ModelAdmin.queryset and ModelAdmin.formfield_for_foreignkey. From the docs:

The queryset method on a ModelAdmin returns a QuerySet of all model instances that can be edited by the admin site. One use case for overriding this method is to show objects owned by the logged-in user:

class MyModelAdmin(admin.ModelAdmin):     def queryset(self, request):         qs = super(MyModelAdmin, self).queryset(request)         if request.user.is_superuser:             return qs         return qs.filter(author=request.user) 

The formfield_for_foreignkey method on a ModelAdmin allows you to override the default formfield for a foreign keys field. For example, to return a subset of objects for this foreign key field based on the user:

class MyModelAdmin(admin.ModelAdmin):     def formfield_for_foreignkey(self, db_field, request, **kwargs):         if db_field.name == "car":             kwargs["queryset"] = Car.objects.filter(owner=request.user)         return super(MyModelAdmin, self).formfield_for_foreignkey(db_field, request, **kwargs) 

This uses the HttpRequest instance to filter the Car foreign key field to only display the cars owned by the User instance.

[update]

Sorry, I failed to read the "filter" part. In Django >= 1.4 you can pass a subclass of django.contrib.admin.SimpleListFilter in the list_filter argument list, which you can use in order to override the lookups and queryset methods.

from datetime import date  from django.contrib import admin from django.utils.translation import ugettext_lazy as _  class DecadeBornListFilter(admin.SimpleListFilter):     # Human-readable title which will be displayed in the     # right admin sidebar just above the filter options.     title = _('decade born')      # Parameter for the filter that will be used in the URL query.     parameter_name = 'decade'      def lookups(self, request, model_admin):         """         Returns a list of tuples. The first element in each         tuple is the coded value for the option that will         appear in the URL query. The second element is the         human-readable name for the option that will appear         in the right sidebar.         """         return (             ('80s', _('in the eighties')),             ('90s', _('in the nineties')),         )      def queryset(self, request, queryset):         """         Returns the filtered queryset based on the value         provided in the query string and retrievable via         `self.value()`.         """         # Compare the requested value (either '80s' or '90s')         # to decide how to filter the queryset.         if self.value() == '80s':             return queryset.filter(birthday__gte=date(1980, 1, 1),                                 birthday__lte=date(1989, 12, 31))         if self.value() == '90s':             return queryset.filter(birthday__gte=date(1990, 1, 1),                                 birthday__lte=date(1999, 12, 31))  class PersonAdmin(admin.ModelAdmin):     list_filter = (DecadeBornListFilter,)