Flask Tutorial #5 - Sessions

Step-by-Step Tutorial: Implementing Sessions in Flask

1. Introduction to Sessions

   • Sessions are used for quick access to information between different pages of a website.
   • Think of a session as a way to store data while the user is on the website, and it gets erased once the user logs out or leaves the website.

2. Setting Up Session Data

   • Import the session module in Flask.
   • Inside a POST request (e.g., login or submit button), set up session data based on the user input.

     user = request.form['user']
     session['user'] = user
     

   • This code snippet stores the user's name in the session.

3. Retrieving Session Data

   • To retrieve the stored session data on another page, use the following code:

     user = session.get('user')
     

   • Check if the session exists before accessing it to ensure the user is logged in.

4. Handling Session Encryption

   • Define a secret key to encrypt and decrypt session data. Add this line at the beginning of your Flask app:

     app.secret_key = 'your_secret_key_here'
     

   • The secret key is crucial for encrypting and decrypting session data.

5. Clearing Session Data

   • Create a function to remove specific data from the session when a user logs out.

     session.pop('user', None)
     

   • Redirect the user to the login page after clearing the session data.

6. Implementing Permanent Sessions

   • Define how long you want a session to last using permanent_session_lifetime in Flask.

     app.permanent_session_lifetime = timedelta(days=5)
     

   • Make a session permanent by setting session.permanent = True when a user logs in.

7. Best Practices

   • Avoid storing sensitive data in sessions.
   • Store only necessary information in sessions, and retrieve additional data from the database when needed.

8. Testing the Implementation

   • Test the login functionality by entering a username and submitting the form.
   • Check if the session data persists when you revisit the website.
   • Log out to ensure the session data is cleared.

9. Conclusion

   • Sessions in Flask are useful for storing temporary data across different pages.
   • Remember to handle session data securely and avoid storing sensitive information in sessions.

By following these steps, you can effectively implement sessions in your Flask application for seamless user experience and data management.