python——集合

 集合要求里面的元素，只能放可哈希的元素，元素不重复，去重，无序的 集合本身时不可哈希的， set作用：关系测试和去重
     set1 = {"xiaohua","huahua","yang","xiaohua"}
     print(set1)#{'huahua', 'xiaohua', 'yang'}去重，多次打印顺序也不一样
     列表去重
     l1 = [1,2,3,3,4,5,1]
     print(list(set(l1)))#[1, 2, 3, 4, 5]先把列表转换集合，再把集合转换列表
     增删查，不能修改，因为没有顺序，没有索引
 增加
     set1 = {"xiaohua","huahua","yang","xiaohua"}
     set1.add("long")
     print(set1)#{'huahua', 'yang', 'long', 'xiaohua'}
     set1.update("abd")
     print(set1)#{'a', 'yang', 'xiaohua', 'd', 'long', 'b', 'huahua'}迭代增加 删除
     set1 = {"xiaohua","huahua","yang","xiaohua"}
     set1.pop()#不可填写元素，随机删除
     print(set1)
     set1.remove("xiaohua")#按照元素删除
     print(set1)#打印{'yang', 'huahua'}去重加删除的元素，剩下两个元素
     set1.clear()#清空元素
     print(set1)#打印set()代表集合
     del set1#全部删除
     print(set1) 查看
     set1 = {"xiaohua","huahua","yang","xiaohua"}
     for i in set1:
         print(i)#只能通过for循环查看 交集 &
     a = {1,2,3,4,5,6}
     b = {3,4,5,6,7,8}
     print(a & b)#打印{3, 4, 5, 6} 并集 |
     a = {1,2,3,4,5,6}
     b = {3,4,5,6,7,8}
     print(a | b)#打印{1, 2, 3, 4, 5, 6, 7, 8}
 差集 -
     a = {1,2,3,4,5,6}
     b = {3,4,5,6,7,8}
     print(a - b)#打印{1, 2}
     print(b - a)#打印{8, 7} 反交集 ^
     a = {1,2,3,4,5,6}
     b = {3,4,5,6,7,8}
     print(a ^ b)#打印{1, 2, 7, 8}
     print(b ^ a)#打印{1, 2, 7, 8} 父子集 一个集合元素是否包含另外一个集合元素
     a = {3,4,5,6}
     b = {3,4,5,6,7,8}
     print(a > b)#打印False
     print(a < b)#打印True