How to solve the Codewars's Array.diff
Today I try to solve the algorithm problem of codewars.
Your goal in this kata is to implement a difference function, which subtracts one list from another and returns the result.
It should remove all values from list a, which are present in list b.
array_diff([1,2],) == 
array_diff([1,2,2,2,3],) == [1,3]
 : built-in list type.
append() : adds a single item to the existing list.
def array_diff(a, b): result =  for i in a: if i not in b: result.append(i) return result