Extracted source code for "Intro to Python"

extract.py

from django.conf.urls import url, include
from django.contrib import admin
from django.db import models
from rest_framework import serializers, viewsets, routers

# DATA MODEL: expected to be in `models.py`
class Flavor(models.Model):
    name = models.CharField(max_length=30)

    def __str__(self):
        return self.name


class Topping(models.Model):
    name = models.CharField(max_length=30)

    def __str__(self):
        return self.name


class Order(models.Model):
    flavor = models.ForeignKey('Flavor', on_delete=models.DO_NOTHING)
    topping = models.ForeignKey('Topping', on_delete=models.DO_NOTHING)

    def __str__(self):
        return "Someone ordered {} topped with {}".format(self.flavor, self.topping)


# SERIALIZERS: handle content negotiation, generally goes `serializers.py` to reduce clutter
class FlavorSerializer(serializers.HyperlinkedModelSerializer):
    class Meta:
        model = Flavor
        fields = ('name', 'url',)

class ToppingSerializer(serializers.HyperlinkedModelSerializer):
    class Meta:
        model = Topping
        fields = ('name', 'url',)

class OrderSerializer(serializers.HyperlinkedModelSerializer):
    order_string = serializers.SerializerMethodField()

    class Meta:
        model = Order
        fields = ('order_string', 'topping', 'flavor')

    def get_order_string(self, obj):
        return "Someone ordered {} topped with {}".format(obj.flavor, obj.topping)

# VIEWS: Handle responding to HTTP web requests, go in `views.py`
class OrderViewSet(viewsets.ModelViewSet):
    queryset = Order.objects.all()
    serializer_class = OrderSerializer
    
class ToppingViewSet(viewsets.ModelViewSet):
    queryset = Topping.objects.all()
    serializer_class = ToppingSerializer
    
class FlavorViewSet(viewsets.ModelViewSet):
    queryset = Flavor.objects.all()
    serializer_class = FlavorSerializer

# ROUTERS: go in a `urls.py` file generally
# Defines the paths given for each ViewSet
router = routers.DefaultRouter()
router.register(r'flavors', FlavorViewSet)
router.register(r'toppings', ToppingViewSet)
router.register(r'orders', OrderViewSet)

# url pattern is django's way of defining routes
urlpatterns = [
    url(r'^', include(router.urls)),
    url(r'^admin/', admin.site.urls),
]