How do you define a variable that you can’t assign a value to yet? You use None
.
None
is a special value in Python. It is unique (there can’t be two different None
s) and immutable (you can’t update None
or assign new attributes to it).
none_var = None if none_var: print("Hello!") else: print("Goodbye") # Prints "Goodbye"
None
is falsy, meaning that it evaluates to False
in an if
statement, which is why the above code prints “Goodbye”. None
is also unique, which means that you can test if something is None
using the is
keyword.
# first we define session_id as None session_id = None if session_id is None: print("session ID is None!") # this prints out "session ID is None!" # we can assign something to session_id if active_session: session_id = active_session.id # but if there's no active_session, we don't send sensitive data if session_id is not None: send_sensitive_data(session_id)
Above we initialize our session_id
to None
, then set our session_id
if there is an active session. Since session_id
could either be None
we check if session_id
is None
before sending our sensitive data.
Instructions
Grab a new review using get_next_review()
. Save the results into a variable called review
.
Check if there is a review
by comparing it against None
. If review
contains a value that isn’t None
, submit it by calling the function submit_review()
with review
as an argument.