Filtering Django Admin by Null/Is Not Null

Question

I have a simple Django model like:

class Person(models.Model):
    referrer = models.ForeignKey(\'self\', null=True)
    ...

In this model\

Answer 1

Since Django 1.4 brings some changes to filters, I thought I save someone the time I just spent modifying the code from Cerin's accepted answer to work with Django 1.4 rc1.

I have a model that has TimeField(null=True) named "started" and I wanted to filter for null and non-null values, so it's prety much the same problem as OP.
So, here is what worked for me...

Defined (actually included) these in admin.py:

from django.contrib.admin.filters import SimpleListFilter

class NullFilterSpec(SimpleListFilter):
    title = u''

    parameter_name = u''

    def lookups(self, request, model_admin):
        return (
            ('1', _('Has value'), ),
            ('0', _('None'), ),
        )

    def queryset(self, request, queryset):
        kwargs = {
        '%s'%self.parameter_name : None,
        }
        if self.value() == '0':
            return queryset.filter(**kwargs)
        if self.value() == '1':
            return queryset.exclude(**kwargs)
        return queryset



class StartNullFilterSpec(NullFilterSpec):
    title = u'Started'
    parameter_name = u'started'

Than just used them in ModelAdmin:

class SomeModelAdmin(admin.ModelAdmin):
    list_filter =  (StartNullFilterSpec, )

Answer 2

There has been a ticket bouncing around for this for 4 years (https://code.djangoproject.com/ticket/5833). It missed the 1.3 milestone, but has reached new feature status and presumably has found it's way into trunk. If you don't mind running off of trunk, you can use it now. The patch is supposedly 1.3 compatible, though, so you can probably get by with just patching your currently installation.

Answer 3

there is a simple way:

class RefererFilter(admin.SimpleListFilter):
    title = 'has referer'
    # Parameter for the filter that will be used in the URL query.
    parameter_name = 'referer__isnull'

    def lookups(self, request, model_admin):
        return (
            ('False', 'has referer'),
            ('True', 'has no referer'),
        )

    def queryset(self, request, queryset):
        if self.value() == 'False':
            return queryset.filter(referer__isnull=False)
        if self.value() == 'True':
            return queryset.filter(referer__isnull=True)

Then just used them in ModelAdmin:

class PersonAdmin(admin.ModelAdmin):
    list_filter =  (RefererFilter,) 

Answer 4

After Django 3.1 you can use EmptyFieldListFilter:

class MyAdmin(admin.ModelAdmin):
    list_filter =  (
        ("model_field", admin.EmptyFieldListFilter),
    )

Answer 5

A snippet with a better explanation might be this. Django 1.4 will ship with a simplified filter mechanism.

Answer 6

I have a simpler version of frnhr's answer, which actually filters on __isnull condition. (Django 1.4+):

from django.contrib.admin import SimpleListFilter

class NullListFilter(SimpleListFilter):
    def lookups(self, request, model_admin):
        return (
            ('1', 'Null', ),
            ('0', '!= Null', ),
        )

    def queryset(self, request, queryset):
        if self.value() in ('0', '1'):
            kwargs = { '{0}__isnull'.format(self.parameter_name) : self.value() == '1' }
            return queryset.filter(**kwargs)
        return queryset

Then also:

class StartNullListFilter(NullListFilter):
    title = u'Started'
    parameter_name = u'started'

and finally:

class SomeModelAdmin(admin.ModelAdmin):
    list_filter =  (StartNullListFilter, )

I personally don't like to trash my admin.py with dozens of classes, so I came up with such a helper function:

def null_filter(field, title_=None):
    class NullListFieldFilter(NullListFilter):
        parameter_name = field
        title = title_ or parameter_name
    return NullListFieldFilter

Which I can later apply as in:

class OtherModelAdmin(admin.ModelAdmin):
    list_filter =  (null_filter('somefield'), null_filter('ugly_field', _('Beautiful Name')), )