Sessions

Remarks#

Sessions are derived from dictionaries which means they will work with most common dictionary methods.

Using the sessions object within a view

First, ensure you have imported sessions from flask

from flask import session

To use session, a Flask application needs a defined SECRET_KEY.

app = Flask(__name__)
app.secret_key = 'app secret key'

Sessions are implemented by default using a cookie signed with the secret key. This ensures that the data is not modified except by your application, so make sure to pick a secure one! A browser will send the cookie back to your application along with each request, enabling the persistence of data across requests.

To use a session you just reference the object (It will behave like a dictionary)

@app.route('/')
def index():
    if 'counter' in session:
        session['counter'] += 1
    else:
        session['counter'] = 1
    return 'Counter: '+str(session['counter'])

To release a session variable use pop() method.

session.pop('counter', None)

Example Code:

from flask import Flask, session

app = Flask(__name__)
app.secret_key = 'app secret key'

@app.route('/')
def index():
    if 'counter' in session:
        session['counter'] += 1
    else:
        session['counter'] = 1
    return 'Counter: '+str(session['counter'])

if __name__ == '__main__':
    app.debug = True
    app.run()