Views and URLs

Learn how to create views that handle user requests and configure URL routing in Django.

What are Views?

Views are Python functions or classes that: - Receive web requests - Process data (often from models) - Return HTTP responses (HTML, JSON, etc.)

Views are the "controller" in Django's MVC pattern.

Function-Based Views

Simple views written as functions:

# myapp/views.py
from django.http import HttpResponse
from django.shortcuts import render

def index(request):
    return HttpResponse("Hello, World!")

def about(request):
    return HttpResponse("About Page")

Request Object

The request parameter contains information about the HTTP request:

def my_view(request):
    # Request method (GET, POST, etc.)
    method = request.method

    # GET parameters
    name = request.GET.get('name', 'Guest')

    # POST data
    if request.method == 'POST':
        email = request.POST.get('email')

    # User information
    user = request.user

    return HttpResponse(f"Hello, {name}")

URL Configuration

Map URLs to views:

App URLs

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

urlpatterns = [
    path('', views.index, name='index'),
    path('about/', views.about, name='about'),
]

Include in Project URLs

# myproject/urls.py
from django.contrib import admin
from django.urls import path, include

urlpatterns = [
    path('admin/', admin.site.urls),
    path('', include('myapp.urls')),
]

URL Patterns

Basic Patterns

urlpatterns = [
    path('', views.home),              # /
    path('about/', views.about),       # /about/
    path('contact/', views.contact),   # /contact/
]

URL Parameters

Capture values from URLs:

# myapp/urls.py
urlpatterns = [
    path('post/<int:post_id>/', views.post_detail),
    # Matches: /post/123/
    # post_id = 123
]

# myapp/views.py
def post_detail(request, post_id):
    return HttpResponse(f"Post ID: {post_id}")

Multiple Parameters

urlpatterns = [
    path('post/<int:year>/<int:month>/', views.post_archive),
    # Matches: /post/2024/01/
]

def post_archive(request, year, month):
    return HttpResponse(f"Archive: {year}/{month}")

String Parameters

urlpatterns = [
    path('user/<str:username>/', views.user_profile),
    # Matches: /user/john/
]

def user_profile(request, username):
    return HttpResponse(f"User: {username}")

Slug Parameters

urlpatterns = [
    path('post/<slug:slug>/', views.post_detail),
    # Matches: /post/my-first-post/
]

def post_detail(request, slug):
    return HttpResponse(f"Post: {slug}")

URL Names

Give URLs names for easy referencing:

# myapp/urls.py
urlpatterns = [
    path('', views.index, name='index'),
    path('about/', views.about, name='about'),
    path('post/<int:post_id>/', views.post_detail, name='post_detail'),
]

Reverse URLs

Get URL from name:

from django.urls import reverse

# In views
url = reverse('post_detail', args=[123])
# Returns: '/post/123/'

# In templates
{% url 'post_detail' post.id %}

Rendering Templates

Return HTML instead of plain text:

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

def index(request):
    return render(request, 'myapp/index.html')

def post_detail(request, post_id):
    context = {
        'post_id': post_id,
        'title': 'My Post',
    }
    return render(request, 'myapp/post_detail.html', context)

Template Location

Create templates in:

myapp/
    templates/
        myapp/
            index.html
            post_detail.html

Passing Data to Templates

Using Context Dictionary

def index(request):
    context = {
        'title': 'Home Page',
        'posts': Post.objects.all(),
        'user': request.user,
    }
    return render(request, 'myapp/index.html', context)

Using locals()

def index(request):
    title = 'Home Page'
    posts = Post.objects.all()
    return render(request, 'myapp/index.html', locals())

Class-Based Views

More powerful, reusable views:

ListView

Display a list of objects:

# myapp/views.py
from django.views.generic import ListView
from .models import Post

class PostListView(ListView):
    model = Post
    template_name = 'myapp/post_list.html'
    context_object_name = 'posts'
    paginate_by = 10

DetailView

Display a single object:

from django.views.generic import DetailView

class PostDetailView(DetailView):
    model = Post
    template_name = 'myapp/post_detail.html'
    context_object_name = 'post'

URL Configuration for Class Views

# myapp/urls.py
from django.urls import path
from .views import PostListView, PostDetailView

urlpatterns = [
    path('posts/', PostListView.as_view(), name='post_list'),
    path('post/<int:pk>/', PostDetailView.as_view(), name='post_detail'),
]

HTTP Methods

Handling GET and POST

def contact(request):
    if request.method == 'POST':
        # Process form submission
        name = request.POST.get('name')
        email = request.POST.get('email')
        message = request.POST.get('message')

        # Process data...

        return HttpResponse("Thank you for your message!")
    else:
        # Display form
        return render(request, 'myapp/contact.html')

Redirects

Redirect to another URL:

from django.shortcuts import redirect
from django.urls import reverse

def my_view(request):
    # Redirect to URL
    return redirect('/about/')

    # Redirect using name
    return redirect('about')

    # Redirect with reverse
    return redirect(reverse('post_detail', args=[123]))

Complete Examples

Simple Blog Views

# myapp/views.py
from django.shortcuts import render, get_object_or_404
from .models import Post

def post_list(request):
    posts = Post.objects.filter(status='published').order_by('-created_at')
    context = {
        'posts': posts,
    }
    return render(request, 'myapp/post_list.html', context)

def post_detail(request, post_id):
    post = get_object_or_404(Post, id=post_id, status='published')
    context = {
        'post': post,
    }
    return render(request, 'myapp/post_detail.html', context)

URL Configuration

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

urlpatterns = [
    path('', views.post_list, name='post_list'),
    path('post/<int:post_id>/', views.post_detail, name='post_detail'),
]

get_object_or_404

Safely get object or return 404:

from django.shortcuts import get_object_or_404

# Instead of:
try:
    post = Post.objects.get(id=post_id)
except Post.DoesNotExist:
    return HttpResponseNotFound()

# Use:
post = get_object_or_404(Post, id=post_id)

URL Namespaces

Organize URLs when using multiple apps:

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

app_name = 'blog'

urlpatterns = [
    path('', views.index, name='index'),
]

# Usage:
# {% url 'blog:index' %}
# reverse('blog:index')

Best Practices

Use URL names: Makes URLs maintainable
Organize views: Group related views together
Use get_object_or_404: Better error handling
Separate GET and POST: Clear logic separation
Use class-based views: For common patterns
Keep views thin: Move logic to models or separate functions

Common Mistakes

1. Forgetting to Include URLs

# ❌ Wrong
# Created myapp/urls.py but didn't include in project urls.py

# ✅ Correct
# myproject/urls.py
urlpatterns = [
    path('', include('myapp.urls')),
]

2. Wrong URL Pattern

# ❌ Wrong
path('post/<int:post_id>', views.post_detail),  # Missing trailing slash

# ✅ Correct
path('post/<int:post_id>/', views.post_detail),

3. Not Using get_object_or_404

# ❌ Wrong
post = Post.objects.get(id=post_id)  # Raises exception if not found

# ✅ Correct
post = get_object_or_404(Post, id=post_id)  # Returns 404 if not found

Practice Exercise

Create views and URLs for:

Home page view that lists all posts
Post detail view that shows a single post
About page view
Contact page view (GET shows form, POST processes it)
URL patterns with proper names
Use get_object_or_404 for detail views

What's Next?

Now that you understand views and URLs, learn to:

Create Templates - Build HTML pages with Django template language
Work with Forms - Handle user input
Use Template Inheritance - Reuse HTML structure
Add Static Files - Include CSS and JavaScript

Previous Tutorial: Models and Databases
Next Tutorial: Templates