How to build a basic Django URL shortener

Django is a Python-based Model View Controller (MVC) web framework that allows us to build fast and efficient websites. Its decoupled architecture facilitates easy scalability, and its powerful caching framework significantly speeds up web application response times.

Note: The /usercode directory is the default workspace directory on the Educative platform to build your application.

Define host names that your application is allowed to serve: Set ALLOWED_HOSTS = ['*'] in the /usercode/urlshortener/urlshortener/settings.py file to allow accepting requests from any domain or set ALLOWED_HOSTS = ['<specific_url>'] to restrict requests to a certain domain only.

Step 2: Define the URL model

Create the URL model: In the /usercode/urlshortener/shortener/models.py file, define a simple model to store the input and respective shortened URLs in the database:

from django.db import models
import string
import random
class URL(models.Model):
    # Fields for the original URL and the shortened code
    original_url = models.URLField()
    short_code = models.CharField(max_length=6, unique=True)
    # Custom save method to ensure a short code is generated if not provided
    def save(self, *args, **kwargs):
        if not self.short_code:
            self.short_code = self._create_unique_short_code()   # Generate short code if not already set
        super(URL, self).save(*args, **kwargs)
    # Method to create a unique 6-character short code
    def _create_unique_short_code(self):
        characters = string.ascii_letters + string.digits
        while True:
            short_code = ''.join(random.choices(characters, k=6))
            if not URL.objects.filter(short_code=short_code).exists():
                break
        return short_code
    def __str__(self):
        # Return the original URL when the instance is represented as a string
        return self.original_url

Defining the URL model

In the above code, there's an integral function generate_short_code() that's responsible for generating shortened URLs against the provided URL. Here's the line-by-line breakdown:
- Line 18: This defines characters as a combination of both letters and digits.
- Line 20-21: This generates short_code using the random.choices() function from our defined set of characters for 6 characters. If the generated short_code already exists in the database, it outputs it; otherwise, it regenerates it to ensure uniqueness.
- Line 22: This returns the unique short_code.

Run migrations to create the database table: Run the following commands in the terminal to create the tables:

from django.shortcuts import render, get_object_or_404, redirect
from django.http import HttpResponse
from .models import URL
# View function to handle URL shortening
def shorten_url(request):
    if request.method == 'POST':
        original_url = request.POST['original_url']  # Get the original URL from POST data
        url, created = URL.objects.get_or_create(original_url=original_url)  # Get or create URL the object
        short_url = request.build_absolute_uri(url.short_code)  # Build the short URL using absolute URI
        return render(request, 'index.html', {'short_url': short_url})  # Render template with short URL
    return render(request, 'index.html')  # Render default template for GET requests
# View function to redirect to original URL
def redirect_url(request, short_code):
    url = get_object_or_404(URL, short_code=short_code)  # Get the URL object by short code or return 404
    return redirect(url.original_url)  # Redirect to the original URL associated with the short code

Processing and forwarding requests

<!DOCTYPE html>
<html>
<body>
    <div class="container">
        <h1>Welcome to the URL Shortener</h1>
        <!-- Form to submit the original URL -->
        <form method="post">
            <h2>Shorten Your URL</h2>
            {% csrf_token %}
            <input type="url" name="original_url" placeholder="Enter URL" required>
            <button type="submit">Shorten</button>
        </form>
        {% if short_url %}
        <!-- Display the short URL if available -->
        <div class="short-url">
            <p>Short URL: <a href="{{ short_url }}">{{ short_url }}</a></p>
        </div>
        {% endif %}
    </div>
</body>
</html>

Designing the front end to input a URL and display its shortened version

How to build a basic Django URL shortener

Components in MVC vs. MVT

Working with Django

Prerequisites

Installing Django

Django URL shortening application

Step 1: Set up the Django project

Step 2: Define the URL model

Step 3: Create views

Step 4: Map URLs to views

Step 5: Create a simple template

Step 6: Run the server

Conclusion

Purpose	Responsible Component in MVC	Responsible Component in MVT
Storing and maintaining data	Model	Model
Providing interactive endpoint to the user	View	Template
Processing and forwarding requests	Controller	View