from django.db import models class Author(models.Model): name = models.CharField(max_length=100) age = models.IntegerField() friends = models.ManyToManyField('self', blank=True) def __str__(self): return self.name class Publisher(models.Model): name = models.CharField(max_length=255) num_awards = models.IntegerField() duration = models.DurationField(blank=True, null=True) def __str__(self): return self.name class Book(models.Model): isbn = models.CharField(max_length=9) name = models.CharField(max_length=255) pages = models.IntegerField() rating = models.FloatField() price = models.DecimalField(decimal_places=2, max_digits=6) authors = models.ManyToManyField(Author) contact = models.ForeignKey(Author, models.CASCADE, related_name='book_contact_set') publisher = models.ForeignKey(Publisher, models.CASCADE) pubdate = models.DateField() def __str__(self): return self.name class Store(models.Model): name = models.CharField(max_length=255) books = models.ManyToManyField(Book) original_opening = models.DateTimeField() friday_night_closing = models.TimeField() def __str__(self): return self.name