30-seconds-of-code/snippets/difference.md

difference

Returns the difference between two arrays.

Create a set from b, then use list comprehension to only keep values not contained in b

def difference(a, b):
    b = set(b)
    return [item for item in a if item not in b]

difference([1, 2, 3], [1, 2, 4]) # [3]