Python: elif or new if?

Question

What is better to use:

if var in X:
    #do_whatever
elif (var in Y):
    #do_whatever2

or:

if var in X:
    #do_whatever
i         


        

Answer 1

If the second statement is impossible if the first one is true (as is the case here, since you said var can't be in both X and Y), then you should be using an elif. Otherwise, the second check will still run, which is a waste of system resources if you know it's going to false.