Check if Session Key is set

Question

I am attempting to create a relatively simple shopping cart in Django. I am storing the cart in request.session['cart']. Therefore, I'll need to access the data in this session when anything is added to it. However, if the session is not already set, I cannot access it without receiving an error. Is there any way to check if a session is set, so that it can be set if it doesn't exist?

Answer 1

I assume that you want to check if a key is set in session, not if a session is set (don't know what the latter means). If so:

You can do:

if key not in request.session:
    # Set it.

In your case:

if 'cart' not in request.session:
    # Set it.

EDIT: changed the code snippet to use key not in rather than not key in. Thanks @katrielalex.

Answer 2

You can use the get-method on the session dictionary, it will not throw an error if the key doesn't exist, but return none as a default value or your custom default value:

cart = request.session.get('cart')
cart = request.session.get('cart', 'no cart')