1 from django.db import models

     2 

     3 

     4 class Part(models.Model):

     5     name = models.CharField(max_length=20)

     6 

     7     class Meta:

     8         ordering = ('name',)

     9 

    10     def __unicode__(self):

    11         return self.name

    12 

    13 class Car(models.Model):

    14     name = models.CharField(max_length=20)

    15     default_parts = models.ManyToManyField(Part)

    16     optional_parts = models.ManyToManyField(Part, related_name='cars_optional')

    17 

    18     class Meta:

    19         ordering = ('name',)

    20 

    21     def __unicode__(self):

    22         return self.name

    23 

    24 class SportsCar(Car):

    25     price = models.IntegerField()

    26 

    27 class Person(models.Model):

    28     name = models.CharField(max_length=20)

    29     fans = models.ManyToManyField('self', related_name='idols', symmetrical=False)

    30     friends = models.ManyToManyField('self')

    31 

    32     class Meta:

    33         ordering = ('name',)

    34 

    35     def __unicode__(self):

    36         return self.name