list1 = [1,2,3,4,4,4]
set1 = set(list1)
print(set1)
set2 = {1,2,4}#不寫K-V型別的，預設就是set集合
set3 = set([1,2,'1'])#必須要加中括號，與上面不一樣，兩種方法都是建立set集合，後者強轉
print(type(set2))
print(set3)

list1 = {1,2,3,4,5}
list2 = {3,4,5,6,7}
print(list1.union(list2))#並集
print(list1.intersection(list2))#交集
print(list1.difference(list2))#等同於list1-list2
print(list2.difference(list1))#等同於list2-list1

list1 = {1,2,3}
list2 = {1,2}
print(list2.issubset(list1))#判斷list2是否是list1的子集，等同於list2 < list1
print()

list1 = {1,2,3}
list1.add(4)
print(list1)
list1.update([5,6])#必須是集合
print(list1)
list1.remove(1)
print(list1)

控制檯：

{1, 2, 3, 4}
<class 'set'>
{'1', 1, 2}
{1, 2, 3, 4, 5, 6, 7}
{3, 4, 5}
{1, 2}
{6, 7}
True
{1, 2, 3, 4}
{1, 2, 3, 4, 5, 6}
{2, 3, 4, 5, 6}