How can I compare two lists in python and return not matches

Question

I would like to return values from both lists that not in the other one:

bar = [ 1,2,3,4,5 ]
foo = [ 1,2,3,6 ]

returnNotMatches( a,b )

would r

Answer 1

This should do

def returnNotMatches(a, b):
    a = set(a)
    b = set(b)
    return [list(b - a), list(a - b)]

And if you don't care that the result should be a list you could just skip the final casting.