Setting and reading cookies in Flask - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What is the output of this Flask route when setting a cookie?

Consider this Flask route that sets a cookie named user with value alice. What will the response headers include?

Flask

from flask import Flask, make_response
app = Flask(__name__)

@app.route('/')
def index():
    resp = make_response('Hello World')
    resp.set_cookie('user', 'alice')
    return resp

A The response will include a Set-Cookie header with 'user=alice'

B The response will include a Set-Cookie header with 'user=alice; Max-Age=3600'

C The response will not include any Set-Cookie header

D The response will include a Set-Cookie header with 'user=alice; HttpOnly; Secure'

💡 Hint

Check how set_cookie works by default without extra parameters.

By default, set_cookie sets a cookie with the given name and value. No extra flags like HttpOnly, Secure, or Max-Age are added unless specified.

❓ state_output

intermediate

What value does the Flask route read from the cookie?

Given this Flask route that reads a cookie named session_id, what will be returned if the cookie is not set?

Flask

from flask import Flask, request
app = Flask(__name__)

@app.route('/read')
def read_cookie():
    session = request.cookies.get('session_id', 'none')
    return f'Session: {session}'

A KeyError exception

B Session:

C Session: None

D Session: none

💡 Hint

Look at the default value provided to get method.

The get method returns the default value 'none' if the cookie is missing, so the returned string is 'Session: none'.

📝 Syntax

advanced

Which option correctly sets a cookie with a 1-hour expiration?

Choose the correct Flask code snippet that sets a cookie named token with value abc123 that expires in 3600 seconds.

A resp.set_cookie('token', 'abc123', maxage=3600)

B resp.set_cookie('token', 'abc123', expires=3600)

C resp.set_cookie('token', 'abc123', max_age=3600)

D resp.set_cookie('token', 'abc123', expire=3600)

💡 Hint

Check the exact parameter name for cookie expiration in Flask's set_cookie.

The correct parameter is max_age (with underscore). Other options are invalid or misspelled.

🔧 Debug

advanced

Why does this Flask code fail to read the cookie?

Given this Flask route, why does it always print Cookie not found even if the user cookie is set?

Flask

from flask import Flask, request
app = Flask(__name__)

@app.route('/check')
def check_cookie():
    if 'User' in request.cookies:
        return f"User: {request.cookies['User']}"
    else:
        return 'Cookie not found'

A Cookies must be accessed with get() method, not by key

B Cookie keys are case-sensitive; 'User' is not the same as 'user'

C Flask does not support reading cookies from request

D The cookie is not sent because the route is missing @app.before_request

💡 Hint

Check the case of the cookie key used in the condition and in the return statement.

Cookie keys are case-sensitive. The code checks for 'User' (uppercase) when the cookie is 'user' (lowercase), so the condition fails.

🧠 Conceptual

expert

What happens if you set a cookie with the Secure flag but access the site over HTTP?

In Flask, if you set a cookie with secure=True, what will happen when the client accesses the site over plain HTTP?

A The cookie will not be sent by the browser on HTTP requests

B The cookie will be sent normally on HTTP and HTTPS

C The cookie will be deleted immediately by the browser

D The server will reject the request due to missing secure cookie

💡 Hint

Think about what the Secure flag means for cookies in browsers.

The Secure flag tells browsers to only send the cookie over HTTPS connections. On HTTP, the cookie is not sent.