def union_list(l1, l2): result = [] if not l1: result.extend(l2) return result if not l2: result.extend(l1) return result result.extend(l1) for i in set(l1+l2): if i not in l1: result.append(i) return result set(l1+l2) 也可以达到以上目的,但是会重新排序.上述程序保留l1的顺序.