Prefetch using queryset #djangotip02

queries.py

# $ python app/manage.py shell
from django.db.models import Prefetch
from .models import Category


def categories_list_active_subcategories_using_prefetch_queryset():
    categories_qs = Category.objects.prefetch_related(
        Prefetch(
            'subcategories',
            queryset=Category.objects.filter(is_active=True),
        )
    )

    categories = []

    for category in categories_qs:
        subcategories = [sub.name for sub in category.subcategories.all()]

        categories.append({
            'name': category.name,
            'is_active': category.is_active,
            'subcategories': subcategories
        })

    return categories