URLs in Django - potatoscript/django GitHub Wiki

When you visit a website, the URL in your browser's address bar corresponds to a specific page or resource on the site. In Django, URLs are used to map a web request (like a click on a link) to a view (a function that processes the request and returns a response).

Step 1: What Are URLs in Django?

In Django, URLs are how we link views to specific paths (web addresses) on our site. Each URL pattern is tied to a view, which will return the content of that URL when someone visits it.

Example:

When you visit http://127.0.0.1:8000/, Django can show you the homepage.
If you visit http://127.0.0.1:8000/about/, Django can show you the "About" page.

Step 2: Setting Up URL Patterns

In Django, URL patterns are defined in a special file called urls.py. When a request is made to the server, Django checks this file to see if the URL matches any patterns defined.

Let's see how to create a simple URL pattern:

Create a urls.py file in your app directory. This file will store all the URL patterns specific to your app. If you created a blog app, the file might look like this:

blog/
└── urls.py  # Contains URL patterns for the blog app

Define URL patterns in urls.py by mapping URLs to views:

# blog/urls.py
from django.urls import path
from . import views  # Import the views from the blog app

urlpatterns = [
    path('', views.post_list, name='post_list'),  # Default homepage for blog posts
    path('about/', views.about, name='about'),  # Another page, like About
]

Here:

path('', views.post_list, name='post_list'): This means that when someone visits the homepage (/), Django will call the post_list view.
path('about/', views.about, name='about'): This means when someone visits /about/, Django will call the about view.

Step 3: Linking to Views in `views.py`

Now we need to create the views that Django will call when users visit the URLs we’ve defined.

Create the views in views.py. This file will contain functions that handle each page request.

# blog/views.py
from django.shortcuts import render

def post_list(request):
    # This function will return all blog posts
    return render(request, 'blog/post_list.html')  # Render a template for posts

def about(request):
    # This function will render the About page
    return render(request, 'blog/about.html')  # Render a template for the About page

Each view function:

Takes a request as an argument.
Uses the render() function to return an HTML template.

Step 4: Adding URL Configuration to the Main Project

The main urls.py file (located in your project folder, e.g., mysite/urls.py) is where we include the URL configurations from each app.

You need to include the app’s URLs into the main project’s urls.py file so that Django knows where to find the URL patterns for the blog app.

Open mysite/urls.py.
Add an include() function to bring in the blog app’s URLs.

# mysite/urls.py
from django.contrib import admin
from django.urls import path, include  # include is used to bring in URLs from apps

urlpatterns = [
    path('admin/', admin.site.urls),
    path('', include('blog.urls')),  # Include the blog app URLs here
]

Step 5: Creating Templates for the Views

Next, let’s create HTML templates for the pages you’re displaying with the views.

Create a templates folder inside your blog app:

blog/
└── templates/
    └── blog/
        ├── post_list.html  # Template for displaying blog posts
        └── about.html      # Template for the About page

Add some content to the templates:

`post_list.html`:

<!DOCTYPE html>
<html>
<head>
    <title>Blog Posts</title>
</head>
<body>
    <h1>Welcome to the Blog!</h1>
    <ul>
        <li><a href="/">Home</a></li>
        <li><a href="/about/">About</a></li>
    </ul>
    <h2>Blog Posts</h2>
    <p>Here is a list of blog posts...</p>
</body>
</html>

`about.html`:

<!DOCTYPE html>
<html>
<head>
    <title>About</title>
</head>
<body>
    <h1>About Us</h1>
    <p>Welcome to our website!</p>
    <ul>
        <li><a href="/">Home</a></li>
        <li><a href="/about/">About</a></li>
    </ul>
</body>
</html>

Step 6: Testing Your URLs

Once you’ve set up everything, start the server and test the URLs:

python manage.py runserver

Go to http://127.0.0.1:8000/ to see the home page of blog posts.
Go to http://127.0.0.1:8000/about/ to see the About page.

Step 7: Using Dynamic URLs

Django also allows you to make dynamic URLs. This means you can capture values from the URL and use them in your views.

For example, let’s say we want to view a specific blog post by its ID.

Modify the urls.py file to accept an ID in the URL:

# blog/urls.py
from django.urls import path
from . import views

urlpatterns = [
    path('', views.post_list, name='post_list'),
    path('about/', views.about, name='about'),
    path('post/<int:id>/', views.post_detail, name='post_detail'),  # Dynamic URL with an ID
]

Create the post_detail view:

# blog/views.py
from django.shortcuts import render

def post_list(request):
    return render(request, 'blog/post_list.html')

def about(request):
    return render(request, 'blog/about.html')

def post_detail(request, id):
    # In a real project, you'd fetch the post from the database using the id
    return render(request, 'blog/post_detail.html', {'id': id})

Create the post_detail.html template:

<!DOCTYPE html>
<html>
<head>
    <title>Post Detail</title>
</head>
<body>
    <h1>Post ID: {{ id }}</h1>
    <p>Here is the detailed content for post {{ id }}...</p>
</body>
</html>

Now, if you visit http://127.0.0.1:8000/post/1/, Django will display the details for the post with ID 1.