How to persist sessions after closing the browser in Flask?

By default, the session object in Flask remains in place until the browser is closed.

However, if you want to change the life of the session object, define the PERMANENT_SESSION_LIFETIME configuration variable after creating the Flask app:

import datetime
app.config['PERMANENT_SESSION_LIFETIME'] = timedelta(minutes=1)

When setting the data in the session, specify that the sessions should be permanent (time will be based on PERMANENT_SESSION_LIFETIME):

# Save the form data to the session object
session['email'] = request.form['email_address']
session.permanent = True

For more, check out Sessions in Flask.