python expression for this: max_value = max(firstArray) that is not in secondArray

Question

Hi. I wasn't sure if there was any good way of doing this. But I thought I'd give stackoverflow a try :)

I have a list/array with integers, and a second array also with integers. I want to find the max value from the first list, but the value can not be in the second array.

Is there any "fancy" way in python to put this down to one expression?
max_value = max(firstArray) that is not in secondArray

Answer 1

Here's one way:

max_value = [x for x in sorted(first) if x not in second][0]

It's less efficient than sorting then using a for loop to test if elements are in the second array, but it fits on one line nicely!

Answer 2

Use sets to get the values in firstArray that are not in secondArray:

max_value = max(set(firstArray) - set(secondArray))