session.session_key is None for signed_cookies sessions on first request

[rwmcfa1]

SessionBase defines:

def _get_session_key(self):

return self._session_key

and sets up a property, session_key to use it

session_key = property(_get_session_key)

signed_cookies.SessionStore overrides _get_session_key and comments as to why.

the problem is that the property, session_key calls the parent class method (SessionBase) rather than the signed_cookies.SessionStore version. that's not destructive in this case since the parent class one just returns the current value, but it causes things that look for the session_key (request.session.session_key) to get the wrong answer (None) on the first request. subsequent requests will see the correct value.

fix, though maybe less than ideal, is to re-define the property at the bottom of signed_cookies so that the descendant class's method will be called.

session_key = property(_get_session_key)

[Aymeric Augustin]

By design you can't access the session key until you save the session.

I've explained why in ​this discussion.

signed_cookies.SessionStore.save does self._session_key = self._get_session_key(), which resolves your problem.