If you’re reading this article, it is very likely you are a serious Python developer or at least dabble with the language. If you happen to be a web developer, you probably have already used or at least heard about Django. Django is a pretty awesome web framework. And in this post, I am going to highlight a few key features that I absolutely love about Django. Along with Django, I will also discuss why I love DRF, the very popular REST API development framework for Django. Lately, these two have become indispensable parts of my life as a web developer and I feel it’s very important that I credit them for their awesomeness and spread the words!

Why I love Django?

• I can quickly generate a project skeleton using the django-admin command. There is management commands to generate apps too.
• I absolutely love Django’s project structure. It is very well organized and meaningful. A project is composed of reusable apps and the apps can self contain the codes and resources they need/use. The idea of reusable apps is very handy. There are plenty of open source apps that you can plug into your project and extend them as necessary. This allows us to reuse codes and get things done faster.
• Django’s way of handling database access makes perfect sense to me. I define models, then automatically generate migrations from those. The migrations are written in Python, so I can adjust or tweak if necessary, programmatically. The Model definitions can be introspected by other parts of the framework to generate Admin UIs or API end points automagically – this is a huge win as we will see.
• Django has a very powerful DB routing mechanism that allows us to use multiple databases and programmatically control the access to them. We can totally control which database is read from, which database is written to, for each app and each model.
• The URL routing portion also makes great sense. There’s a main route configuration per project. We can add app specific routes to this configuration by include-ing them. You can add namespaces to these included ones. The namespacing gets rids of naming conflict when importing routes from 3rd party apps.
• For simple views, the function based views are pretty efficient. But there’s also class based views for more control and dealing with complex needs.
• The Generic Class Views are awesome! You can define ListView, CreateView, UpdateView, DetailView or a DeleteView. You pass them the Model to use and some configuration options, they will handle your CRUD operations for you while you can focus your time and concentration on preparing the templates. These have allowed me to build custom CRUD views very very fast. The generic views are very customizable, so you can alter the database queries, pagination, form fields, values passed to the template. If you’re still writing your own business logic for CRUD views, it’s time you took generic class views for a ride. What I like most is that generic views are generated dynamically. It’s not like scaffolding or code generation. In the case of scaffolding, when you need to add an extra field, you need to modify your model, controller, template, form etc. In class based generic views, you just update your model and everything is updated dynamically.
• Talking about CRUD views, often you won’t even need to build them. The Django Admin interface takes in your models and generates a beautiful (and powerful) admin interface from them. The admin interface is very customizable. You can add custom actions, filtering, templates and whats not! Once you master Django’s admin interface, you will probably never need to build CRUD views from scratch. Many of my projects use Django Admin with high client satisfaction. And remember what we said about reusable apps and open source packages? There are several packages which provide alterations or replacement for the built in admin interface. You can plug in one of those for a different taste!
• Management commands are easy to write and comes in very handy for simple tasks. When you install apps, they can provide useful management commands too. One of my favourite management command is “dbshell” which allows me to drop into the database’s command line without remembering the login details.
• Django Templates are pretty awesome too. The syntax is quite similar to Jinja2 (which inspired many templating languages across different platforms). You can extend the templates by writing your own tags and filters. And there’s of course a backend for direct Jinja2 support.
• Django is quite mature and the eco system is thriving. There’s a django package for almost everything you would need. There are many 3rd party packages for extending the different parts of Django. There are blogs, forums, cms etc apps which you can plug into your current project to add those functionality. Python also has a vast libraries for numerous purposes. It’s easy to plug them in when we need.
• Oh, and did I forget to mention the documentation? Django documentation is superb. Very well written and covers almost everything in the framework. I would say Django Docs is one of the best out there.

The above mentioned features are just a few that I can remember right now. Django has been very pleasant to develop in. I have always felt a productivity boost as well as mental satisfaction when working with Django. Every time I faced a challenge, I have found a very simple solutions to it.

Why I love Django REST Framework?

• Browsable APIs on the web – this is one of the best things about DRF. DRF provides very nice web browsable views for your API end points. These views allow HTML forms to submit data to the APIs. At the same time, they also show sample JSON payload for those requests. You can submit a request through the forms/json input and get back a response. So this is pretty much self documentation of the APIs. I have worked with front end and mobile developers (who consumed my APIs) and they absolutely loved the web browsable interface. In most cases, I didn’t even need to provide any API docs to them, they managed to figure things out for themselves. And if you would still want Swagger, there are 3rd party extensions for that too.
• The ModelViewSet is like those admin views for Django. You can quickly generate CRUD based REST APIs out of your models using this class.
• There is APIView which provides get, post, put, delete etc methods representing the HTTP verbs. You can extend APIView and provide business logic for these methods to quickly craft your APIs. There are mixins and some preset class based views to generate these methods based on querysets.
• But don’t be satisfied just yet, ViewSets take things one step further. When you use APIView, you need to create two routes (for example one for /users and one for /users/1) but with ViewSets allow us to focus more on the business logic while forgetting about the route management. ViewSet is a class based view that has methods like list, retrieve, create, update, destroy – instead of the http verbs. The ViewSet methods allows us to cover all the REST operations in just one class. We add the view set to a router and the router generates all the necessary underlying django routes, ready to be included in a urlconf. And as mentioned earlier, the ModelViewSet is a ViewSet that generates these methods from a Model (queryset)
• Authentication is baked in the framework. It’s very easy to setup different authentications for your APIs. The permission management is also very simple. The framework integrates nicely with some third party packages to support authentication methods which are not supported by the framework by default.
• The framework is very customizable. We can easily extend the functionality to suit our needs. It’s all very simple, quite like the simplicity of Django!
• The documentation is excellent. Adequate examples and very clearly described.

The only thing I am not completely happy with DRF is creating nested routes (/user/1/comment/2) is still pretty difficult/cumbersome. But the way DRF adds features quickly, I hope this will be resolved soon, in some upcoming releases!

Helping These Projects Grow

Django and DRF both are open source projects and are the results of many hours of dedication from kind hearted OSS enthusiasts. Today, we can build and maintain awesome projects because Django and DRF exists. We should all consider giving something back to these projects, in return to the benefits they have brought us!

We can help these projects by contributing codes, helping with translations, answering questions, promoting the projects or making donations.

Here you can learn how to contribute to Django — https://docs.djangoproject.com/en/dev/internals/contributing/

Django Software Foundation accepts donations here — https://www.djangoproject.com/fundraising/

DRF Contribution guide here — http://www.django-rest-framework.org/topics/contributing/

In this post, we would like to see how we can limit user accesses to our Django views.

Login Required & Permission Required Decorators

If you have worked with Django, you probably have used the login_required decorator already. Adding the decorator to a view limits access only to the logged in users. If the user is not logged in, s/he is redirected to the default login page. Or we can pass a custom login url to the decorator for that purpose.

Let’s see an example:

There’s another nice decorator – permission_required which works in a similar fashion:

Awesome but let’s learn how do they work internally.

How do they work?

We saw the magic of the login_required and permission_required decorators. But we’re the men of science and we don’t like to believe in magic. So let’s unravel the mystery of these useful decorators.

Here’s the code for the login_required decorator:

By reading the code, we can see that the login_required decorator uses another decorator – user_passes_test which takes/uses a callable to determine whether the user should have access to this view. The callable must accept an user instance and return a boolean value. user_passes_test returns a decorator which is applied to our view.

If we see the source of permission_required, we would see something quite similar. It also uses the same user_passes_test decorator.

Building Our Own Decorators

Now that we know how to limit access to a view based on whether the logged in user passes a test, it’s quite simple for us to build our own decorators for various purposes. Let’s say we want to allow access only to those users who have verified their emails.

Now we can use the decorator to a view like:

Users who have verified their email addresses will be able to access this view. And if they didn’t, they will be redirected to the login view. Using the reason query string, we can display a nice message explaining what’s happening.

Please note, we have used two decorators on the same view. We can use multiple decorators like this to make sure the user passes all the tests we require them to.

I assume you are already familiar with Docker and it’s use cases. If you haven’t yet started using Docker, I strongly recommend you do soon.

I have a Django application that I want to dockerize it for local development. I am also new to Docker, so everything I do in this post might not be suitable for your production environment. So please do check Docker best practices for production apps. This tutorial is meant to be a basic introduction to Docker. In this post, I am going to use Docker Machine and Docker Compose. You can get them by installing the awesome Docker Toolbox.

Components Breakdown

Before we start, we need to break down our requirements so we can individually build the required components. For my particular application, we need these:

1. Django App Server
2. MySQL Database Server
3. Redis Server

We will build images for these separately so we can create individual containers and link them together to compose our ultimate application. We shall build our Django App server and use pre-built images for MySQL and Redis.

Building the Django App Server

Before we begin, let’s talk Dockerfiles. Dockerfiles are scripts to customize our docker builds. It allows us control and flexibility over how we build the images for our applications. We will use our custom Dockerfile to build the Django app server.

To build an image for a Django application we need to go through these following steps:

• Select a Linux image, we choose Ubuntu
• Install required packages for the distro.
• Install Python packages which are required for the app
• Provide a default command to run and ports to expose

Here’s the Dockerfile we shall use:

So what are we doing here:

• We’re choosing phusion/baseimage as our base image. It’s a barebone image based on Ubuntu. Ubuntu by default comes with many packages which we don’t need to run inside docker. This base image gets rid of those and provides a very lean and clean image to start with.
• We just provide a Maintainer name
• We set DEBIAN_FRONTEND to be non interactive. This will not display any interactive prompts during the build process. Since the docker build process is automated, we really don’t have any way to interact during it. So we disable interaction. And as you might have guessed already ENV sets an environment variable.
• We install some packages we shall need.
• We copy our requirements.txt file to /app/src/requirements.txt, change the work directory and install the packages using pip. ADD is used to copy any files or directories to the container while it builds. You might wonder why we didn’t copy over our entire project – that’s because we want to use docker for our development. We will use a nice featire of Docker which would allow us to mount our local directories directly inside the container. Doing this, we would not need to copy files every time they change. More on this will come later.
• We change directory to /app/src/lisp and run the runall management command. This command runs the Django default server along with some other services my application needs. But usually we would want to just do runserver
• We EXPOSE port 8000

If you go through the Dockerfile References you will notice – we can do a lot more with Dockerfiles.

Docker Compose and Linking Services

As we mentioned earlier, we shall use pre-built images for MySQL and Redis. We could build them ourselves too but why not take advantage of the well maintained images from the generous folks in the docker community?

We can link multiple docker containers to compose a final application. We can do that using the docker command manually. But Docker Compose is a very nice tool which allows us to define the services we need in a very easy to read syntax. With docker compose, we don’t need to run them manually, we can just use simple commands to do complex docker magic! Here’s our docker-compose.yml file:

In our docker-compose file, we define 3 components:

• For the web, we pass the path to Dockerfile to build key. We ask to restart always and define volumes to mount. .:/app/src means – mount the current directory on my OS X as /app/src/ on the container. We also define which ports to expose and which containers should be linked with it
• We also define the mysql and redis components with respective configurations. Note that we define the pre-built image name in the image key. Please make sure the volume paths exist and are accessible.

You can consult the Compose File Reference for more details.

Running The Services

To run the application, we can do:

Please note, the Django server might throw errors if the MySQL / Redis server takes time to initialize. So I usually run them separately:

Database Configuration for Django

Our MySQL server is running on the IP of the Docker Machine. You need to use this IP address in your Django settings file. To get the IP of a docker machine, type in:

Creating Initial Databases

We can pass a MYSQL_DATABASE environment value to the mysql image so the database is created when creating the service. Or we can also connect to the docker machine manually and create our databases.