fixtures fixtures are a way of loading data into the database in bulk fixure data can be stored in any serializable format including json and xml fixtures are identified by name and are stored in either a directory named fixtures in the application directory or in one of the directories named in the fixturedirs setting
import uuid

from django.contrib.auth.models import Permission
from django.contrib.contenttypes.fields import GenericForeignKey
from django.contrib.contenttypes.models import ContentType
from django.db import models


class Category(models.Model):
    title = models.CharField(max_length=100)
    description = models.TextField()

    class Meta:
        ordering = ("title",)

    def __str__(self):
        return self.title


class Article(models.Model):
    headline = models.CharField(max_length=100, default="Default headline")
    pub_date = models.DateTimeField()

    class Meta:
        ordering = ("-pub_date", "headline")

    def __str__(self):
        return self.headline


class Blog(models.Model):
    name = models.CharField(max_length=100)
    featured = models.ForeignKey(
        Article, models.CASCADE, related_name="fixtures_featured_set"
    )
    articles = models.ManyToManyField(
        Article, blank=True, related_name="fixtures_articles_set"
    )

    def __str__(self):
        return self.name


class Tag(models.Model):
    name = models.CharField(max_length=100)
    tagged_type = models.ForeignKey(
        ContentType, models.CASCADE, related_name="fixtures_tag_set"
    )
    tagged_id = models.PositiveIntegerField(default=0)
    tagged = GenericForeignKey(ct_field="tagged_type", fk_field="tagged_id")

    def __str__(self):
        return '<%s: %s> tagged "%s"' % (
            self.tagged.__class__.__name__,
            self.tagged,
            self.name,
        )


class PersonManager(models.Manager):
    def get_by_natural_key(self, name):
        return self.get(name=name)


class Person(models.Model):
    objects = PersonManager()
    name = models.CharField(max_length=100, unique=True)

    class Meta:
        ordering = ("name",)

    def __str__(self):
        return self.name

    def natural_key(self):
        return (self.name,)


class SpyManager(PersonManager):
    def get_queryset(self):
        return super().get_queryset().filter(cover_blown=False)


class Spy(Person):
    objects = SpyManager()
    cover_blown = models.BooleanField(default=False)


class ProxySpy(Spy):
    class Meta:
        proxy = True


class Visa(models.Model):
    person = models.ForeignKey(Person, models.CASCADE)
    permissions = models.ManyToManyField(Permission, blank=True)

    def __str__(self):
        return "%s %s" % (
            self.person.name,
            ", ".join(p.name for p in self.permissions.all()),
        )


class Book(models.Model):
    name = models.CharField(max_length=100)
    authors = models.ManyToManyField(Person)

    class Meta:
        ordering = ("name",)

    def __str__(self):
        authors = " and ".join(a.name for a in self.authors.all())
        return "%s by %s" % (self.name, authors) if authors else self.name


class PrimaryKeyUUIDModel(models.Model):
    id = models.UUIDField(primary_key=True, default=uuid.uuid4)


class NaturalKeyManager(models.Manager):
    def get_by_natural_key(self, key):
        return self.get(key=key)


class NaturalKeyThing(models.Model):
    key = models.CharField(max_length=100, unique=True)
    other_thing = models.ForeignKey(
        "NaturalKeyThing", on_delete=models.CASCADE, null=True
    )
    other_things = models.ManyToManyField(
        "NaturalKeyThing", related_name="thing_m2m_set"
    )

    objects = NaturalKeyManager()

    def natural_key(self):
        return (self.key,)

    def __str__(self):
        return self.key


class CircularA(models.Model):
    key = models.CharField(max_length=3, unique=True)
    obj = models.ForeignKey("CircularB", models.SET_NULL, null=True)

    objects = NaturalKeyManager()

    def natural_key(self):
        return (self.key,)


class CircularB(models.Model):
    key = models.CharField(max_length=3, unique=True)
    obj = models.ForeignKey("CircularA", models.SET_NULL, null=True)

    objects = NaturalKeyManager()

    def natural_key(self):
        return (self.key,)