Login view and template in Django - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What does this Django login view render on GET request?

Consider this Django view code for login. What template does it render when accessed with a GET request?

Django

from django.shortcuts import render, redirect
from django.contrib.auth import authenticate, login

def login_view(request):
    if request.method == 'POST':
        username = request.POST.get('username')
        password = request.POST.get('password')
        user = authenticate(request, username=username, password=password)
        if user is not None:
            login(request, user)
            return redirect('home')
        else:
            return render(request, 'login.html', {'error': 'Invalid credentials'})
    else:
        return render(request, 'login.html')

A Redirects to 'home' on GET request

B Renders 'login.html' template without any context on GET

C Renders 'home.html' template on GET

D Raises a 404 error on GET request

💡 Hint

Check what happens when the request method is not POST.

The view checks if the request method is POST to process login. For GET requests, it renders 'login.html' without extra context.

📝 Syntax

intermediate

Which option correctly includes CSRF token in Django login template?

In Django templates, to protect POST forms from CSRF attacks, which snippet correctly includes the CSRF token inside the form?

Django

<form method="post" action="">
    <!-- CSRF token here -->
    <input type="text" name="username" />
    <input type="password" name="password" />
    <button type="submit">Login</button>
</form>

A {% csrf_token %}

B {{ csrf_token }}

C <input type="hidden" name="csrfmiddlewaretoken" value="{{ csrf_token }}">

D <csrf_token />

💡 Hint

Django uses a special template tag for CSRF tokens.

Django requires the template tag {% csrf_token %} inside POST forms to add the CSRF token input automatically.

❓ state_output

advanced

What is the value of 'error' in context after failed login POST?

Given this login view, what will be the value of 'error' in the context passed to the template after a failed login attempt?

Django

def login_view(request):
    if request.method == 'POST':
        username = request.POST.get('username')
        password = request.POST.get('password')
        user = authenticate(request, username=username, password=password)
        if user is not None:
            login(request, user)
            return redirect('home')
        else:
            return render(request, 'login.html', {'error': 'Invalid credentials'})
    else:
        return render(request, 'login.html')

A 'Invalid credentials'

B KeyError because 'error' is missing

C Empty string ''

D None

💡 Hint

Look at the else block inside the POST method.

When authentication fails, the view renders 'login.html' with context {'error': 'Invalid credentials'}.

🔧 Debug

advanced

Why does this login view raise a TypeError?

Identify the cause of the TypeError in this Django login view snippet.

Django

def login_view(request):
    if request.method == 'POST':
        username = request.POST['username']
        password = request.POST['password']
        user = authenticate(username=username, password=password)
        if user:
            login(request, user)
            return redirect('home')
        else:
            return render(request, 'login.html', {'error': 'Invalid credentials'})
    return render(request, 'login.html')

A redirect called without parentheses

B login function called with wrong number of arguments

C authenticate missing 'request' argument causes TypeError

D request.POST['username'] raises KeyError

💡 Hint

Check the signature of authenticate in Django 4+.

In Django 4+, authenticate requires the request argument. Omitting it causes a TypeError.

🧠 Conceptual

expert

Which option best describes the purpose of 'login' function in Django views?

In Django, what is the main effect of calling the 'login(request, user)' function inside a view?

A It logs the user out and clears the session

B It creates a new user account in the database

C It redirects the user to the login page

D It sets the user ID in the session to mark the user as authenticated

💡 Hint

Think about what happens after a successful login.

The login function saves the user's ID in the session so Django knows the user is authenticated on future requests.