How to join two arrays and subtract the same elements?

Question

Python

There is an array[1,2,2], and the second [1]
It is necessary that an array would be obtained only with twos without ones.
You need to do it with def(a, b)

Answer 1

def cross(a, b):
    return [x for x in a if x not in b]

Answer 2

Do you need a check that duplicates can be in both the first and the second list? If necessary, you need to make two passes:

a=[1,2,3,4,4,4,1,1,3]
b=[2,2,5,10,11,3,3]
out1=[x for x in a if x not in b]
print ('Из А отсеяно то, что дублируется в  Б', out1)
out2=[x for x in b if x not in a]
print ('Из Б отсеяно то, что  дублируется в А', out2)
print ('Итого',out1+out2)
Из А отсеяны дубликаты из Б [1, 4, 4, 4, 1, 1]
Из Б отсеяны дубликаты из А [5, 10, 11]
Итого [1, 4, 4, 4, 1, 1, 5, 10, 11]

Answer 3

def x(a,b):
    res = []
    for el in a:
        if el not in b: res.append(el)
    return res

Something like this