input: Write a function to find the union of two lists and return the result as a set. If either list is empty, return the non-empty list as a set.
  def unionList(list1, list2):
      return set(list1 + list2) if list1 and list2 else set(list1) or set(list2)
  assert unionList([1, 2, 3, 4, 5], [3, 4, 5, 6, 7])=={1, 2, 3, 4, 5, 6, 7}
  assert unionList([], [3, 4, 5, 6, 7])=={3, 4, 5, 6, 7}
  assert unionList([1, 2, 3], [])=={1, 2, 3}
  assert unionList([1, 2, 3, 3, 2, 1], [5, 6, 6, 5])=={1, 2, 3, 5, 6}
  assert unionList([], [])==set()
output: def unionList(list1, list2):
      return set(list1 + list2) if list1 and list2 else set(list1) or set(list2)