Combining two lists and removing duplicates, without removing duplicates in original list

Question

I have two lists that i need to combine where the second list has any duplicates of the first list ignored. .. A bit hard to explain, so let me show an example of what the c

Answer 1

first_list = [1, 2, 2, 5]
second_list = [2, 5, 7, 9]

print( set( first_list + second_list ) )