How to Build a USSD App Using Python and Django

Introduction

This tutorial will guide you on how to build your first USSD app.

Tools used

• Python 3
• Django 1.11 - The Web framework for perfectionist with deadlines
• Virtualenv
• Ngrok
• Africastalking API

First of all, we need to create a Virtual environment using a tool known as virtualenv. It is highly recommended and best practice to create a virtual environment before you begin any Python project. Virtualenv isolates your Python set-up on a per-project basis. This means that changes made to one Python project won’t affect another Python project.

Setting up virtualenv

On a Windows, Linux or OS X

mkdir africastalking_demo
cd africastalking_demo

The next step is to make our virtual environment. This will be called environment. Make sure the names you choose for your virtualenv is in lower case with no special characters and spaces.

python3 -m venv environment

Working with Virtual environment

Windows

Enter the africastalking_demo directory

cd  africastalking_demo

Activate the virtual environment

environment\Scripts\activate

Linux and OS X

Enter the africastalking_demo directory

cd africastalking_demo

Activate the virtual environment

source environment/bin/activate

You will know that you have virtualenv started when you see that the prompt in your console is prefixed with (environment)

Then enter into the environment directory

cd environment

To install pip Use

sudo easy_install pip 

In the environment directory with the virtual environment already activated, you can now install django

pip install django~=1.11

After the installation of django, you will need to create a django project

django-admin startproject africastalking_project . 

Take note of the dot after africastalking_project

At this juncture, you can open the africastalking_project in your Text editor

You should see the following files:

• manage.py
• settings.py
• urls.py

This shows that the project was successfully created.

In the settings.py file, add the following

STATIC_ROOT = os.path.join(BASE_DIR, ‘static’)

Creating an application

In the command line

python manage.py startapp demo      

demo is the name of our application. This name is different from the project name

In the settings.py file, you should see something like this;

INSTALLED_APPS = [
this is not empty
]

Add ‘demo’ to the list of apps found in INSTALLED_APPS

INSTALLED_APPS = [
‘demo’
]

In your Text editor, you should see the demo folder. It has the following files

• admin.py
• apps.py
• models.py
• tests.py
• views.py

Type out the code below into views.py

from django.views.decorators.csrf import csrf_exempt
from django.http import HttpResponse

# Create your views here.



@csrf_exempt
def index(request):
    if request.method == 'POST':
        session_id = request.POST.get('sessionId')
        service_code = request.POST.get('serviceCode')
        phone_number = request.POST.get('phoneNumber')
        text = request.POST.get('text')

        response = ""

        if text == "":
            response = "CON What would you want to check \n"
            # response .= "1. My Account \n"
            response += "1. My Phone Number"

        elif text == "1":
            response = "END My Phone number is {0}".format(phone_number)

        return HttpResponse(response)

Let me explain the code above.

You need to define the function that will receive the call from your service code.

We are calling this function index. As in all views functions, the index function will have a request argument.

The first line of code in our function is if request.method == ‘POST’. This line tells python that if a POST is sent to the server, it should do the lines of code that follow.

Normally, you receive a POST from the frontend, when a form is filled by a user. But in the case of the USSD API, the POST information is sent directly to the server whenever a user dials the service code.

The next four lines are variables and we pass the information sent from the USSD API after a user must have dialed the service code.

The response variable is created with an empty string. The if...elif statements followed is what Africastalking recommends and that is how the response screen will appear to the user.

The line if text == " ": means that the user has not sent any request after dialing the USSD code. The response = 'CON What would you want to check line contains a response variable with a string that begins with CON. This is the first message that appears on a User's screen immediately after dialing a USSD code.

According to Africastalking, the first response variable in either a if statement or an elif statement must begin with CON. Hence for every if...elif statement, the first response variable will have a string that begins with CON. The response += "1. My Phone Number" line is the first option that a user can reply with. In this case, we have just one option which is 1. We can have as many options as possible.

The elif text == "1": line means that if a user replies with 1, do the following. The line response ="END My phone number is {0}".format(phoneNumber) is the message that appears on a User screen since the User replied with 1. The END in the string means that's the last message that should after which the connection will the terminated. We have to return a response in our function which is why we have the return HttpResponse(response) line. The built-in Django function HttpResponse allows a view function to return a response. This function is imported in from django.http import HttpResponse. There is one last import that we have to do which is from django.views.decorators.csrf import csrf_exempt. We have to decorate our view function otherwise an error will be returned by Django. According to Django, every POST request must have {% csrf_token %} on the form.But since our POST request is not from a form we have to explicitly inform Django to exempt this particular views function. This is why our function is decorated with @csrf_exempt .

Create an Africastalking account

Navigate to Africastalking site and create an account. Login to your newly created account.

Create an app and you should see something like the image below.

Click on Go to Sandbox app. The next page is similar to the image below.

Click on Create channel This will take you to a page where you will create your own USSD service code. You will also be required to provide a callback url, but for the sake of this tutorial, we will make use of Ngrok. Ngrok is basically a software that provides a public url for accessing our local host. It listens from the same port that your local server is running on.

Install and Use Ngrok

Download ngrok zip file, unzip the file and move it to /usr/local/bin PATH.

Run ngrok in the terminal using the following command.

ngrok http 8000

The default port for Django is 8000, which is what we have used.

Running ngrok takes you to a page where you can copy the generated public url. This url changes every time we run run ngrok.

Starting and Setting up the USSD App

Go to our Django project and locate the settings.py file. Paste the url inside the square brackets

ALLOWED_HOSTS = [ ]

Run the Django server using the following command after you must have activated the virtual environment where the africastalking_demo project is located.

python manage.py runserver

Also Go ahead to Africastalking, the Create a channel page and fill in your ngrok public url.

Click on Launch simulator to test your new USSD app.

Congratulations you just created your first USSD app.

You can follow me on Twitter: @IyanuAshiri. You can also star this project on GitHub.