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],[1]) == [2]

  • array_diff([1,2,2,2,3],[2]) == [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:
    return result
Written on December 10, 2018