1. from django.contrib.auth.models import User

  2. from django.contrib.contenttypes.fields import GenericForeignKey, GenericRelation

  3. from django.contrib.contenttypes.models import ContentType

  4. from django.db import models

  5. 

  6. 

  7. class Book(models.Model):

  8.     title = models.CharField(max_length=50)

  9.     year = models.PositiveIntegerField(null=True, blank=True)

  10.     author = models.ForeignKey(

  11.         User,

  12.         models.SET_NULL,

  13.         verbose_name="Verbose Author",

  14.         related_name="books_authored",

  15.         blank=True,

  16.         null=True,

  17.     )

  18.     contributors = models.ManyToManyField(

  19.         User,

  20.         verbose_name="Verbose Contributors",

  21.         related_name="books_contributed",

  22.         blank=True,

  23.     )

  24.     employee = models.ForeignKey(

  25.         "Employee",

  26.         models.SET_NULL,

  27.         verbose_name="Employee",

  28.         blank=True,

  29.         null=True,

  30.     )

  31.     is_best_seller = models.BooleanField(default=0, null=True)

  32.     date_registered = models.DateField(null=True)

  33.     availability = models.BooleanField(

  34.         choices=(

  35.             (False, "Paid"),

  36.             (True, "Free"),

  37.             (None, "Obscure"),

  38.         ),

  39.         null=True,

  40.     )

  41.     # This field name is intentionally 2 characters long (#16080).

  42.     no = models.IntegerField(verbose_name="number", blank=True, null=True)

  43. 

  44.     def __str__(self):

  45.         return self.title

  46. 

  47. 

  48. class ImprovedBook(models.Model):

  49.     book = models.OneToOneField(Book, models.CASCADE)

  50. 

  51. 

  52. class Department(models.Model):

  53.     code = models.CharField(max_length=4, unique=True)

  54.     description = models.CharField(max_length=50, blank=True, null=True)

  55. 

  56.     def __str__(self):

  57.         return self.description

  58. 

  59. 

  60. class Employee(models.Model):

  61.     department = models.ForeignKey(Department, models.CASCADE, to_field="code")

  62.     name = models.CharField(max_length=100)

  63. 

  64.     def __str__(self):

  65.         return self.name

  66. 

  67. 

  68. class TaggedItem(models.Model):

  69.     tag = models.SlugField()

  70.     content_type = models.ForeignKey(

  71.         ContentType, models.CASCADE, related_name="tagged_items"

  72.     )

  73.     object_id = models.PositiveIntegerField()

  74.     content_object = GenericForeignKey("content_type", "object_id")

  75. 

  76.     def __str__(self):

  77.         return self.tag

  78. 

  79. 

  80. class Bookmark(models.Model):

  81.     url = models.URLField()

  82.     tags = GenericRelation(TaggedItem)

  83. 

  84.     CHOICES = [

  85.         ("a", "A"),

  86.         (None, "None"),

  87.         ("", "-"),

  88.     ]

  89.     none_or_null = models.CharField(

  90.         max_length=20, choices=CHOICES, blank=True, null=True

  91.     )

  92. 

  93.     def __str__(self):

  94.         return self.url
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