Exploring the Django Request-Response Flow

Previously I showed how to set up Django and install on your development environment. Next we need to make it really useful, and that means responding to user requests.

But what actually happens when someone visits a page on your Django site?

Let's look at how Django works under the hood, from incoming request to outgoing response.

It doesn't matter if you're building a blog, a dashboard, or an API, understanding this flow is fundamental for structure in your apps, and to help you debug faster.

What Happens When a User Visits Your Site?

When a user visits a URL on your Django site, here's what happens behind the scenes:

• Django receives the HTTP request from the browser.
• It checks the top-level URL configuration in myproject/urls.py.
• Django tries to match the requested URL pattern to one of the defined path() entries.
• If matched, it either routes directly to a view or includes another URLconf from an app (for modular structure).
• App-level urls.py continues matching any remaining part of the URL.
• Once a matching pattern is found, it points to a view function.
• The view function runs your Python logic (e.g., database queries, calculations).
• The view returns an HttpResponse object—HTML, JSON, a redirect, or an error.
• Django sends this response back to the user's browser.

Handling Path Variables (e.g., /greet/Alice/)

Sometimes you want to use part of the URL as a variable, such as a name or ID.

Step 1: Add a view in greetings/views.py

from django.http import HttpResponse

def home(request):
    html_content = "<h1>Welcome to the App!</h1><p>This is the homepage.</p>"
    return HttpResponse(html_content)

def personalized_greeting(request, name):
    html_content = f"<h1>Hello, {name.capitalize()}!</h1><p>Nice to meet you.</p>"
    return HttpResponse(html_content)

Step 2: Add a URL pattern in greetings/urls.py

from django.urls import path
from . import views

urlpatterns = [
    path('', views.home, name='home'),
    path('<str:name>/', views.personalized_greeting, name='personalized_greeting'),
]

• <str:name> captures part of the URL and passes it to the view.
• Other converters: int:, slug:, uuid:, path:

Handling Query Parameters (e.g., /search?q=django)

Query parameters come after the ? in a URL. They're not part of the path matching.

View example in greetings/views.py

def search(request):
    query = request.GET.get('q', '')
    page = request.GET.get('page', '1')

    html_content = "<h1>Search Results</h1>"
    if query:
        html_content += f"<p>You searched for: <strong>{query}</strong></p>"
    else:
        html_content += "<p>Please provide a search term using ?q=...</p>"

    html_content += f"<p>Showing page: {page}</p>"
    return HttpResponse(html_content)

URL pattern

path('search/', views.search, name='search'),

Redirecting the User

Sometimes you want to send the user to another page (e.g., after submitting a form or accessing a shortcut URL).

View example

from django.http import HttpResponseRedirect
from django.urls import reverse

def go_home(request):
    return HttpResponseRedirect(reverse('home'))

Or shorter, using redirect:

from django.shortcuts import redirect

def go_home(request):
    return redirect('home')

URL pattern

path('go-home/', views.go_home, name='go_home'),

Returning a 404 Not Found

To manually raise a 404 (e.g., when a record doesn’t exist), use:

from django.http import Http404

def show_profile(request, username):
    allowed_users = ['alice', 'bob', 'carol']
    if username not in allowed_users:
        raise Http404("User not found")

    html_content = f"<h1>Profile of {username.capitalize()}</h1>"
    return HttpResponse(html_content)

URL pattern

path('profile/<str:username>/', views.show_profile, name='show_profile'),

If you want to customize the 404 page, create a 404.html template and Django will render it automatically when a 404 is raised.

Testing the Server

Start your server with:

python3 manage.py runserver

Try these in your browser:

• http://127.0.0.1:8000/greetings/Alice/
• http://127.0.0.1:8000/greetings/search/?q=django
• http://127.0.0.1:8000/greetings/go-home/
• http://127.0.0.1:8000/greetings/profile/zorg/ (should show a 404)