Why authentication matters in Flask - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to import the Flask class.

Flask

from flask import [1]
app = [1](__name__)

Drag options to blanks, or click blank then click option'

ASession

BRequest

CBlueprint

DFlask

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'Request' instead of 'Flask' to create the app.

The Flask class is imported to create the app instance.

2fill in blank

medium

Complete the code to protect a route with a login check.

Flask

@app.route('/dashboard')
def dashboard():
    if not session.get('[1]'):
        return 'Please log in first', 401
    return 'Welcome to your dashboard!'

Drag options to blanks, or click blank then click option'

Auser

Blogged_in

Cauthenticated

Dusername

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'user' which may store username but not login status.

The 'logged_in' key in session is commonly used to check if a user is logged in.

3fill in blank

hard

Fix the error in the login function to set the session correctly.

Flask

from flask import session

def login():
    # after verifying user credentials
    session['[1]'] = True
    return 'Logged in successfully!'

Drag options to blanks, or click blank then click option'

Alogged_in

Buser

Cauthenticated_user

Dusername

Attempts:

3 left

💡 Hint

Common Mistakes

Setting 'user' or 'username' to True instead of a boolean flag.

Setting 'logged_in' to True in session marks the user as logged in.

4fill in blank

hard

Fill both blanks to create a dictionary comprehension that stores usernames and their login status.

Flask

user_status = {user: session.get('[1]', False) for user in users if user [2] 'admin'}

Drag options to blanks, or click blank then click option'

Alogged_in

B!=

C==

Dauthenticated

Attempts:

3 left

💡 Hint

Common Mistakes

Using '==' instead of '!=' to exclude 'admin'.

The comprehension checks if users are logged in and excludes 'admin' users.

5fill in blank

hard

Fill all three blanks to create a secure logout function that clears the session and redirects.

Flask

from flask import session, redirect, url_for

def logout():
    session.[1]()
    return redirect(url_for('[2]'))

@app.route('/logout')
def logout_route():
    return logout()

Drag options to blanks, or click blank then click option'

Aclear

Blogin

Cremove

Dhome

Attempts:

3 left

💡 Hint

Common Mistakes

Using session.remove() which does not exist.

Calling session.clear() removes all session data. Redirecting to 'login' page after logout is common.

Practice

1. Why is authentication important in a Flask web application?

easy

A. It speeds up the loading time of web pages.

B. It verifies the identity of users to protect sensitive data.

C. It automatically fixes bugs in the code.

D. It changes the website's color scheme based on user preference.

Solution

1. Step 1: Understand the purpose of authentication

   Authentication checks who the user is by verifying their identity, usually with a username and password.

2. Step 2: Connect authentication to security

   This process protects sensitive data and resources from unauthorized access.

3. Final Answer:

   It verifies the identity of users to protect sensitive data. -> Option B

4. Quick Check:

   Authentication = User identity verification [OK]

Hint: Authentication means checking who the user is [OK]

Common Mistakes:

• Confusing authentication with website speed
• Thinking authentication changes design
• Believing authentication fixes bugs automatically

2. Which of the following is the correct way to protect a Flask route with authentication using Flask-Login?

easy

A. @login_required
def dashboard():
return 'Welcome to your dashboard!'

B. def login_required():
return 'Welcome!'

C. @app.route('/dashboard')
def login_required():
return 'Dashboard'

D. @app.login_required
def dashboard():
return 'Dashboard'

Solution

1. Step 1: Recognize Flask-Login decorator usage

   The correct decorator to protect routes is @login_required placed above the route function.

2. Step 2: Check syntax and function name

   @login_required def dashboard(): return 'Welcome to your dashboard!' correctly uses @login_required above a function named dashboard that returns a welcome message.

3. Final Answer:

   @login_required\ndef dashboard():\n return 'Welcome to your dashboard!' -> Option A

4. Quick Check:

   Use @login_required decorator to protect routes [OK]

Hint: Use @login_required above route functions [OK]

Common Mistakes:

• Using @app.login_required instead of @login_required
• Defining login_required as a function instead of a decorator
• Missing the decorator above the route function

3. Given this Flask route using Flask-Login, what happens when an unauthenticated user tries to access /profile?

@app.route('/profile')
@login_required
def profile():
    return 'User Profile'

medium

A. The user sees 'User Profile' page immediately.

B. The server returns a 404 Not Found error.

C. The user is redirected to the login page.

D. The server crashes with an error.

Solution

1. Step 1: Understand @login_required behavior

   The @login_required decorator checks if the user is logged in before allowing access.

2. Step 2: Identify what happens if user is not logged in

   If the user is not authenticated, Flask-Login redirects them to the login page automatically.

3. Final Answer:

   The user is redirected to the login page. -> Option C

4. Quick Check:

   Unauthenticated access = redirect to login [OK]

Hint: Unauthenticated users get redirected to login page [OK]

Common Mistakes:

• Assuming unauthenticated users see the protected page
• Thinking server returns 404 error
• Believing server crashes on unauthenticated access

4. What is wrong with this Flask route code that tries to protect a page with authentication?

@app.route('/settings')
def settings():
    @login_required
    return 'Settings Page'

medium

A. The code uses @login_required but Flask-Login is not imported.

B. The route decorator @app.route is missing the URL.

C. The function settings() is missing a return statement.

D. The @login_required decorator is incorrectly placed inside the function.

Solution

1. Step 1: Check decorator placement

   Decorators like @login_required must be placed above the function definition, not inside it.

2. Step 2: Verify function syntax

   Placing @login_required inside the function causes a syntax error and does not protect the route.

3. Final Answer:

   The @login_required decorator is incorrectly placed inside the function. -> Option D

4. Quick Check:

   Decorators go above functions, not inside [OK]

Hint: Put decorators above function definitions, never inside [OK]

Common Mistakes:

• Placing decorators inside function body
• Forgetting to import Flask-Login
• Missing return statement in route function

5. You want to create a Flask app where only logged-in users can access the /dashboard route, and users who are not logged in should be redirected to /login. Which of the following code snippets correctly implements this behavior using Flask-Login?

hard

A. from flask_login import login_required

@app.route('/dashboard')
@login_required
def dashboard():
return 'Dashboard Page'

# Flask-Login automatically redirects unauthenticated users to /login

B. @app.route('/dashboard')
def dashboard():
if not current_user.is_authenticated:
return redirect('/login')
return 'Dashboard Page'

C. @app.route('/dashboard')
@login_required
def dashboard():
return redirect('/login')

D. @app.route('/dashboard')
def dashboard():
return 'Dashboard Page'

Solution

1. Step 1: Identify Flask-Login usage for route protection

   Using @login_required decorator from Flask-Login protects the route and handles redirection automatically.

2. Step 2: Check if redirection to /login is automatic

   Flask-Login by default redirects unauthenticated users to the login view, so no manual redirect is needed inside the function.

3. Final Answer:

   from flask_login import login_required @app.route('/dashboard') @login_required def dashboard(): return 'Dashboard Page' # Flask-Login automatically redirects unauthenticated users to /login -> Option A

4. Quick Check:

   @login_required protects route and redirects unauthenticated users [OK]

Hint: Use @login_required; Flask-Login handles redirect automatically [OK]

Common Mistakes:

• Manually redirecting inside the route when @login_required suffices
• Returning redirect inside a protected route without condition
• Not protecting the route at all