Django ORM cookbook

Django ORM cookbook is a set of recipes of how to do things with Django. They take the form of about 50 questions of the form How to do X with Django ORM/Queryset.

We have a set of models which we use across the book for answering these questions.

The models

You plan to write a set of models and an assoicated admin for UMSRA researchers. You come up with two apps entities and events. The models are

Events

from django.db import models
from django.utils.text import slugify
from entities.models import Hero, Villain
from django.contrib.auth.models import User
import uuid

class Epic(models.Model):
    name = models.CharField(max_length=255)
    participating_heroes = models.ManyToManyField(Hero)
    participating_villains = models.ManyToManyField(Villain)

class Event(models.Model):
    id = models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False)
    epic = models.ForeignKey(Epic, on_delete=models.CASCADE)
    details = models.TextField()
    years_ago = models.PositiveIntegerField()

class EventHero(models.Model):
    event = models.ForeignKey(Event, on_delete=models.CASCADE)
    hero = models.ForeignKey(Hero, on_delete=models.CASCADE)
    is_primary = models.BooleanField()

class EventVillain(models.Model):
    event = models.ForeignKey(Event, on_delete=models.CASCADE)
    hero = models.ForeignKey(Villain, on_delete=models.CASCADE)
    is_primary = models.BooleanField()

class UserParent(models.Model):
    user = models.OneToOneField(
        User,
        on_delete=models.CASCADE,
        primary_key=True,
    )
    father_name = models.CharField(max_length=100)
    mother_name = models.CharField(max_length=100)

class Article(models.Model):
    headline = models.CharField(max_length=100)
    pub_date = models.DateField()
    reporter = models.ForeignKey(User, on_delete=models.CASCADE, related_name='reporter')
    slug = models.SlugField()

    def save(self, *args, **kwargs):
        self.slug = slugify(self.headline)
        super(Article, self).save(*args, **kwargs)
    def __str__(self):
        return self.headline

    class Meta:
        ordering = ('headline',)

class TempUser(models.Model):
    first_name = models.CharField(max_length=100)

    class Meta:
        managed = False
        db_table = "temp_user"

class ColumnName(models.Model):
    a = models.CharField(max_length=40,db_column='column1')
    column2 = models.CharField(max_length=50)

    def __str__(self):
        return self.a

Entities

from django.db import models

from django.conf import settings

class Category(models.Model):
    name = models.CharField(max_length=100)

    class Meta:
        verbose_name_plural = "Categories"

    def __str__(self):
        return self.name

class Origin(models.Model):
    name = models.CharField(max_length=100)

    def __str__(self):
        return self.name

class Entity(models.Model):
    GENDER_MALE = "Male"
    GENDER_FEMALE = "Female"
    GENDER_OTHERS = "Others/Unknown"

    name = models.CharField(max_length=100)
    alternative_name = models.CharField(
        max_length=100, null=True, blank=True
    )

    category = models.ForeignKey(Category, on_delete=models.CASCADE)
    origin = models.ForeignKey(Origin, on_delete=models.CASCADE)
    gender = models.CharField(
        max_length=100,
        choices=(
            (GENDER_MALE, GENDER_MALE),
            (GENDER_FEMALE, GENDER_FEMALE),
            (GENDER_OTHERS, GENDER_OTHERS),
        )
    )
    description = models.TextField()

    added_by = models.ForeignKey(settings.AUTH_USER_MODEL,
        null=True, blank=True, on_delete=models.SET_NULL)
    added_on = models.DateField(auto_now=True)

    def __str__(self):
        return self.name

    class Meta:
        abstract = True

class Hero(Entity):

    class Meta:
        verbose_name_plural = "Heroes"

    is_immortal = models.BooleanField(default=True)

    benevolence_factor = models.PositiveSmallIntegerField(
        help_text="How benevolent this hero is?"
    )
    arbitrariness_factor = models.PositiveSmallIntegerField(
        help_text="How arbitrary this hero is?"
    )

    headshot = models.ImageField(null=True, blank=True, upload_to="hero_headshots/")

    # relationships
    father = models.ForeignKey(
        "self", related_name="children", null=True, blank=True, on_delete=models.SET_NULL
    )
    mother = models.ForeignKey(
        "self", related_name="+", null=True, blank=True, on_delete=models.SET_NULL
    )
    spouse = models.ForeignKey(
        "self", related_name="+", null=True, blank=True, on_delete=models.SET_NULL
    )

class HeroProxy(Hero):

    class Meta:
        proxy = True

class Villain(Entity):
    is_immortal = models.BooleanField(default=False)

    malevolence_factor = models.PositiveSmallIntegerField(
        help_text="How malevolent this villain is?"
    )
    power_factor = models.PositiveSmallIntegerField(
        help_text="How powerful this villain is?"
    )
    is_unique = models.BooleanField(default=True)
    count = models.PositiveSmallIntegerField(default=1)

class HeroAcquaintance(models.Model):
    "Non family contacts of a Hero"
    hero = models.OneToOneField(Hero, on_delete=models.CASCADE)

    friends = models.ManyToManyField(Hero, related_name="+")
    detractors = models.ManyToManyField(Hero, related_name="+")
    main_anatagonists = models.ManyToManyField(Villain, related_name="+")

class AllEntity(models.Model):
    name = models.CharField(max_length=100)

    class Meta:
        managed = False
        db_table = "entities_entity"