def f():
a = [1,2,3,4,5]
b = [4,5,6,7,8]

return list(set(a)-set(b))

you are right

hello my code is correct pass the first test but when i presse ATTEMPT i got this message "Execution Timed Out"
Most of the time though this issue is caused by inefficient algorithms. If you see this error multiple times you should try to optimize your code further.
i do it with 5 lines ..!