Django REST Framework Crash Course

Kyle Rich

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Overview
- Quick Introductions
Django
REST and RESTful web APIs
Example project

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Overview
- Quick Introductions
- Django REST Framework
Serializing / deserializing data
Representing data relationships
Grouping functionality in viewsets
Automatic endpoints with routers

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Django4 / 37

Django

- Overview

"The web framework for perfectionists with deadlines."

"Django was invented to meet fast-moving newsroom deadlines, while satisfying the tough requirements of experienced Web developers."

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Django
- Overview
- Common Tools
Authentication
Caching
Logging
Sending emails
Syndication feeds (RSS / Atom)
Pagination
Messages framework
Serialization

Sessions
Sitemaps
Static  files management
Data validation
Templating (DTL, Jinja2, etc.)
Flatpages
Redirects

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REST and RESTful web APIs7 / 37

REST

- What is REST?

REpresentational State Transfer (REST) is an architectural style that describes six constraints.

To the extent that systems conform to the constraints of REST they can be called RESTful.

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REST
- What is REST?
- Constraints
Uniform Interface
Stateless (HATEOAS)
Cacheable
Client-Server
Layered System
Code on Demand (optional)

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REST
- What is REST?
- Constraints
- What it buys us
Performance
Scalability
Simplicity
Modifiability
Visibility
Portability
Reliability

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REST
- What is REST?
- Constraints
- What it buys us
- Web APIs
Resource (noun) based, collections and instances
Use standard HTTP verbs to specify actions
Use HTTP response codes to indicate status
Offer responses in multiple formats (JSON, XML, etc.)

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Example Project: 12 / 37

I love reading, and I use GoodReads to make it a somewhat social experience. But GoodReads isn't perfect. It could be better. Better than good. So I decided to start work on...

Example Project: BetterReads12 / 37

I love reading, and I use GoodReads to make it a somewhat social experience. But GoodReads isn't perfect. It could be better. Better than good. So I decided to start work on...

...BetterReads! Which will be better than GoodReads!

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Serialization
- Publisher
class Publisher(models.Model):
    name = models.CharField(max_length=50, unique=True)
    address = models.TextField()

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Serialization
- Publisher
class Publisher(models.Model):
    name = models.CharField(max_length=50, unique=True)
    address = models.TextField()

class PublisherSerializer(serializers.ModelSerializer):
    class Meta:
        model = models.Publisher

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Note that the serializer knows the model class, and it knows all of the attributes on that class. The ModelSerializer default behavior automatically creates an appropriate serializer field for each attribute on the model

Serialization
- Publisher
class Publisher(models.Model):
    name = models.CharField(max_length=50, unique=True)
    address = models.TextField()

class PublisherSerializer(serializers.ModelSerializer):
    class Meta:
        model = models.Publisher

{
  'address': '12345 S. State Street',
  'id': 1,
  'name': 'Del Rey'
}

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Serialization
- Publisher
- Person
class Person(models.Model):
    first_name = models.CharField(max_length=50)
    last_name = models.CharField(max_length=50)
    email = models.CharField(max_length=50)
    class Meta:
        unique_together = ('first_name', 'last_name')

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The unique_together constraint creates a multi-column index keeping all combinations of first and last names unique.

Serialization
- Publisher
- Person
class Person(models.Model):
    first_name = models.CharField(max_length=50)
    last_name = models.CharField(max_length=50)
    email = models.CharField(max_length=50)
    class Meta:
        unique_together = ('first_name', 'last_name')

class PersonSerializer(serializers.ModelSerializer):
    email = serializers.EmailField()
    class Meta:
        model = models.Person

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The unique_together constraint creates a multi-column index keeping all combinations of first and last names unique.

We can customize the way the email field is serialized by giving it a different serializer field. The EmailField serializer will check for a valid e-mail address before accepting the input.

Serialization
- Publisher
- Person
- Tag
class Tag(models.Model):
    name = models.CharField(max_length=20, unique=True)

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Serialization
- Publisher
- Person
- Tag
class Tag(models.Model):
    name = models.CharField(max_length=20, unique=True)

class TagSerializer(serializers.ModelSerializer):
    books = serializers.SlugRelatedField(
        slug_field='name', many=True
        queryset=models.Book.objects.all())
    class Meta:
        model = models.Tag

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The slug related field alters the way a data relationship is displayed, by simply displaying one of the attributes of the related object. The attribute it shows is specified in the slug_field.

Serialization
- Publisher
- Person
- Tag
- Book
class Book(models.Model):
    name = models.CharField(max_length=100)
    authors = models.ManyToManyField(Person)
    tags = models.ManyToManyField(Tag)
    publisher = models.ForeignKey(Publisher, null=True)
    year = models.IntegerField(null=True)
    in_print = models.BooleanField(default=True)

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Serialization
- Publisher
- Person
- Tag
- Book
class Book(models.Model):
    name = models.CharField(max_length=100)
    authors = models.ManyToManyField(Person)
    tags = models.ManyToManyField(Tag)
    publisher = models.ForeignKey(Publisher, null=True)
    year = models.IntegerField(null=True)
    in_print = models.BooleanField(default=True)

class BookSerializer(serializers.ModelSerializer):
    tags = serializers.SlugRelatedField(
        slug_field='name', many=True,
        queryset=models.Tag.objects.all())
    publisher = serializers.SlugRelatedField(
        slug_field='name', allow_null=True,
        queryset=models.Publisher.objects.all())
    url = serializers.HyperlinkedIdentityField(
        view_name='book-detail')
    class Meta:
        model = models.Book

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The HyperlinkedIdentityField creates a link to the current object's representation. The url field is automatically created with the same field serializer if you subclass HyperlinkedModelSerializer instead of ModelSerializer.

Serialization
- Publisher
- Person
- Tag
- Book
- Book JSON
{
  'authors': [
    1
  ],
  'id': 1,
  'in_print': True,
  'name': 'A Really Good Book',
  'publisher': None,
  'tags': [
    'Fun',
    'Fantasy'
  ],
  'url': 'http://localhost:8000/api/books/1/',
  'year': 2016
}

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Note that authors and tags are both M2M relationships, but they render differently. Is anyone surprised by this?

Serialization
- Publisher
- Person
- Tag
- Book
- Book JSON
- Notes
Serializers render Python objects to plain-text representation (JSON, XML, etc.)

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Serialization
- Publisher
- Person
- Tag
- Book
- Book JSON
- Notes
Serializers render Python objects to plain-text representation (JSON, XML, etc.)

They also parse plain-text representations (JSON, XML, etc.) and convert back to Python objects

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Serialization
- Publisher
- Person
- Tag
- Book
- Book JSON
- Notes
Serializers render Python objects to plain-text representation (JSON, XML, etc.)

They also parse plain-text representations (JSON, XML, etc.) and convert back to Python objects

You can control and override how both of those processes work

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Serialization
- Publisher
- Person
- Tag
- Book
- Book JSON
- Notes
Serializers render Python objects to plain-text representation (JSON, XML, etc.)

They also parse plain-text representations (JSON, XML, etc.) and convert back to Python objects

You can control and override how both of those processes work

Serializer classes give you broad control

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Serialization
- Publisher
- Person
- Tag
- Book
- Book JSON
- Notes
Serializers render Python objects to plain-text representation (JSON, XML, etc.)

They also parse plain-text representations (JSON, XML, etc.) and convert back to Python objects

You can control and override how both of those processes work

Serializer classes give you broad control

Serializer fields give you granular control

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ViewSets20 / 37

ViewSets

- Methods

We're used to talking in terms of HTTP methods

GET
POST
PUT
PATCH
DELETE
OPTIONS
HEAD

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ViewSets

- Methods

- Actions

DRF talks in terms of "actions"

list
create
retrieve
update
delete

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ViewSets

- Methods

- Actions

- Detail View

Detail view is for actions on an instance, or in other words, any time you have the primary key.

/api/books/1/

GET -> retrieve
PUT / PATCH -> update
DELETE -> delete

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ViewSets

- Methods

- Actions

- Detail View

- List View

List view is for actions when you don't have a primary key.

/api/books/

GET -> list
POST -> create

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ViewSets

- Methods

- Actions

- Detail View

- List View

- Grouping

DRF will happily create a view for every action you need with ViewSets.

class PersonViewSet(viewsets.ModelViewSet):
    queryset = models.Person.objects.all()
    serializer_class = serializers.PersonSerializer

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ViewSets

- Methods

- Actions

- Detail View

- List View

- Grouping

DRF will happily create a view for every action you need with ViewSets.

class PersonViewSet(viewsets.ModelViewSet):
    queryset = models.Person.objects.all()
    serializer_class = serializers.PersonSerializer

TagViewSet and PublisherViewSet are virtually identical to PersonViewSet.

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ViewSets

- Methods

- Actions

- Detail View

- List View

- Grouping

- Filtering

Here's the most interesting thing my viewsets do:

class BookViewSet(viewsets.ModelViewSet):
    queryset = models.Book.objects.all()
    serializer_class = serializers.BookSerializer
    filter_fields = ('year', 'in_print', 'authors',
                     'name', 'tags', 'publisher')

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Note that the ModelViewSet creates all five actions, but there are other viewsets that only create the actions for a read-only resource, or you can mix and match them to get the required functionality for a resource.

Routers27 / 37

Routers
- Review
Models created with Django ORM

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Routers
- Review
Models created with Django ORM

Object serialized to representation in desired format

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Routers
- Review
Models created with Django ORM

Object serialized to representation in desired format

Viewsets to interact with each resource

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Routers
- Review
Models created with Django ORM

Object serialized to representation in desired format

Viewsets to interact with each resource

What are we still missing?
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Routers
- Review
- URLs
from django.conf.urls import include, url
from rest_framework import routers
from api import views
api = routers.DefaultRouter()
api.register('books', views.BookViewSet)
api.register('tags', views.TagViewSet)
api.register('publishers', views.PublisherViewSet)
api.register('people', views.PersonViewSet)
urlpatterns = [
    url(r'^', include(api.urls))
]

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Lines of Code
- Just FYI...
There are four files that make up the core of this service.
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Lines of Code
- Just FYI...
There are four files that make up the core of this service.
models.py
serializers.py
views.py
urls.py

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Lines of Code
- Just FYI...
There are four files that make up the core of this service.
models.py
serializers.py
views.py
urls.py

Those four files total 124 lines of code.
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Lines of Code
- Just FYI...
There are four files that make up the core of this service.
models.py
serializers.py
views.py
urls.py

Those four files total 124 lines of code.
Of those, 42 are whitespace.
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Lines of Code
- Just FYI...
There are four files that make up the core of this service.
models.py
serializers.py
views.py
urls.py

Those four files total 124 lines of code.
Of those, 42 are whitespace.
Only 82 are actually doing something.
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Let's play with it!31 / 37

Let's play with it!
- Python requests
Python 3.5.1 (default, Dec  7 2015, 21:59:08)
[GCC 4.2.1 Compatible Apple LLVM 7.0.0
(clang-700.1.76)] on darwin
Type "help", "copyright", "credits" or
"license" for more information.

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Let's play with it!
- Python requests
Python 3.5.1 (default, Dec  7 2015, 21:59:08)
[GCC 4.2.1 Compatible Apple LLVM 7.0.0
(clang-700.1.76)] on darwin
Type "help", "copyright", "credits" or
"license" for more information.

>>> import requests

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Let's play with it!
- Python requests
Python 3.5.1 (default, Dec  7 2015, 21:59:08)
[GCC 4.2.1 Compatible Apple LLVM 7.0.0
(clang-700.1.76)] on darwin
Type "help", "copyright", "credits" or
"license" for more information.

>>> import requests

>>> from pprint import pprint

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Let's play with it!
- Python requests
Python 3.5.1 (default, Dec  7 2015, 21:59:08)
[GCC 4.2.1 Compatible Apple LLVM 7.0.0
(clang-700.1.76)] on darwin
Type "help", "copyright", "credits" or
"license" for more information.

>>> import requests

>>> from pprint import pprint

>>> data = requests.get(
...     'http://localhost:8000/api/people/'
... ).json()

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Let's play with it!
- Python requests
Python 3.5.1 (default, Dec  7 2015, 21:59:08)
[GCC 4.2.1 Compatible Apple LLVM 7.0.0
(clang-700.1.76)] on darwin
Type "help", "copyright", "credits" or
"license" for more information.

>>> import requests

>>> from pprint import pprint

>>> data = requests.get(
...     'http://localhost:8000/api/people/'
... ).json()

>>> pprint(data)
[{'email': 'kyle@mydomain.com',
  'first_name': 'Kyle',
  'id': 1,
  'last_name': 'Rich'}]

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Let's play with it!
- Python requests
- Browsable API
Django REST Framework Browsable API
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Let's play with it!
- Python requests
- Browsable API
- CLI Client
Custom CLI Client
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Let's play with it!
- Python requests
- Browsable API
- CLI Client
- Swagger
Swagger
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Questions?36 / 37

Resources

This talk https://git.io/drfcc
REST API Tutorial http://www.restapitutorial.com/
REST on Wikipedia
Django REST Framework documentation http://www.django-rest-framework.org/
RemarkJS Markdown based presentation framework http://remarkjs.com

Please leave feedback!

https://joind.in/talk/40348

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