I recently came across a seemingly simple situation, which I could not find a nice pythonic way to write. I wanted to ask SO for their solutions and which would be fastest.

I have two arrays, say `Arr1 = [-1, 0, 1, 2, 3]` and `Arr2 = [1, 2, 3]`. I want to get an array of the elements in Arr1 but not in Arr2. Again, super simple situation, but it turned out to be tricky to implement.

I tried variations of `[x in Arr1 and not Arr2]`, but because `not` evaluates to a Boolean this raises an error. I feel like python has a really nice and clean solution to this, but it is escaping my mind.

(My solution was `filter(lambda x: x not in Arr2, Arr1)`. It works, but it isn't a satisfying solution. Does SO have a more pythonic way?)