Alphabet filter in Django admin

alphabet_filter_django_admin.py

"""
Suppose you have a django model in models.py:

class Animal(models.Model):
    animal_name = models.CharField(u'name', max_length=255)

to create an alphabetfilter in django admin panel you need to create a class which inherits
admin.SimpleListFilter in admin.py

here is the code snippet below for admin.py file
"""
import string
from django.contrib import admin

class AlphabetFilter(admin.SimpleListFilter):
    title = 'alphabet'
    parameter_name = 'alphabet'

    def lookups(self, request, model_admin):
        abc = list(string.ascii_lowercase)
        return ((c.upper(), c.upper()) for c in abc)

    def queryset(self, request, queryset):
        if self.value():
            # filter specific attr of the model
            return queryset.filter(animal_name__startswith=self.value())


class AnimalAdmin(admin.ModelAdmin):
    list_display = ['name',]
    list_filter = (AlphabetFilter,)
admin.site.register(Animal, AnimalAdmin)