Session lifetime in Flask - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding Flask session lifetime default behavior

In Flask, what is the default behavior of the session lifetime if you do not explicitly set PERMANENT_SESSION_LIFETIME?

A The session expires after 5 minutes automatically.

B The session lasts only until the browser is closed (non-permanent session).

C The session lasts for 31 days by default.

D The session lasts forever until manually cleared.

💡 Hint

Think about what happens when you close your browser without setting anything.

By default, Flask sessions are not permanent, so they last only until the browser is closed. This means the session cookie is a browser session cookie.

❓ state_output

intermediate

Effect of setting session.permanent to True

Given this Flask code snippet, what will be the lifetime of the session cookie if PERMANENT_SESSION_LIFETIME is set to 1 day and session.permanent = True is set?

from flask import Flask, session
from datetime import timedelta

app = Flask(__name__)
app.secret_key = 'secret'
app.config['PERMANENT_SESSION_LIFETIME'] = timedelta(days=1)

@app.route('/')
def index():
    session.permanent = True
    session['user'] = 'Alice'
    return 'Session set'

A The session cookie will never expire.

B The session cookie will expire when the browser is closed.

C The session cookie will expire after 1 day, even if the browser is closed.

D The session cookie will expire immediately after the response.

💡 Hint

Setting session.permanent = True changes the cookie type.

When session.permanent is set to True, Flask uses the PERMANENT_SESSION_LIFETIME config to set the cookie expiration. Here it is 1 day.

🔧 Debug

advanced

Why does session not expire as expected?

A developer sets app.config['PERMANENT_SESSION_LIFETIME'] = timedelta(minutes=5) and session.permanent = True in their Flask app. But the session still lasts longer than 5 minutes. What is the most likely reason?

A The session cookie is not being updated on each request, so expiration is not refreshed.

B The developer forgot to set a secret key, so sessions are not saved.

C The server's system clock is incorrect, causing expiration times to be wrong.

D Flask does not support session expiration shorter than 10 minutes.

💡 Hint

Think about how session expiration is refreshed in Flask.

Flask refreshes the session expiration time only when the session cookie is updated. If the cookie is not refreshed on each request, the expiration time remains fixed from the first set.

📝 Syntax

advanced

Correct way to set session lifetime in Flask

Which of the following code snippets correctly sets the Flask session lifetime to 2 hours?

A app.session_lifetime = timedelta(hours=2)

B app.config['SESSION_LIFETIME'] = 2

C session.lifetime = timedelta(hours=2)

D app.config['PERMANENT_SESSION_LIFETIME'] = timedelta(hours=2)

💡 Hint

Check the exact config key Flask uses for session lifetime.

The correct config key is PERMANENT_SESSION_LIFETIME. Other options are invalid or do not exist.

❓ component_behavior

expert

Session lifetime behavior with multiple requests

Consider a Flask app with PERMANENT_SESSION_LIFETIME set to 10 minutes and session.permanent = True. A user makes a request at 12:00, then another at 12:08, and then at 12:15. Assuming the session cookie is updated on each request, at what time will the session expire if the user stops making requests after 12:15?

A The session will expire at 12:25, which is 10 minutes after the last request.

B The session will expire at 12:10, which is 10 minutes after the first request.

C The session will expire at 12:15, immediately after the last request.

D The session will never expire because it is permanent.

💡 Hint

Think about how Flask refreshes the expiration time on each request.

Flask resets the expiration time on each request that updates the session cookie. So the expiration moves forward with each request.