Creating Custom Filters for list_filter in Django Admin

Question

I would like to make custom filters for django admin instead of the normal 'is_staff' and 'is_superuser'. I have read this list_filter in Django docs. Custom Filters work in this way:

from datetime import date

from django.utils.translation import ugettext_lazy as _
from django.contrib.admin import SimpleListFilter

class DecadeBornListFilter(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(ModelAdmin):
    list_filter = (DecadeBornListFilter,)

But i have already made custom functions for list_display like this:

def Student_Country(self, obj):
    return '%s' % obj.country
Student_Country.short_description = 'Student-Country'

Is it possible i could use the custom functions for list_display in list_filter instead of writing a new custom function for list_filter? Any suggestions or improvements are welcome.. Need some guidance on this... Thanks...

Answer 1

You can indeed add custom filters to admin filters by extending SimpleListFilter. For instance, if you want to add a continent filter for 'Africa' to the country admin filter used above, you can do the following:

In admin.py:

from django.contrib.admin import SimpleListFilter

class CountryFilter(SimpleListFilter):
    title = 'country' # or use _('country') for translated title
    parameter_name = 'country'

    def lookups(self, request, model_admin):
        countries = set([c.country for c in model_admin.model.objects.all()])
        return [(c.id, c.name) for c in countries] + [
          ('AFRICA', 'AFRICA - ALL')]

    def queryset(self, request, queryset):
        if self.value() == 'AFRICA':
            return queryset.filter(country__continent='Africa')
        if self.value():
            return queryset.filter(country__id__exact=self.value())

class CityAdmin(ModelAdmin):
    list_filter = (CountryFilter,)