# 2.12 集合

集合（set）是一个无序且不含重复元素的序列。

集合主要用来进行成员关系测试和删除重复元素。

我们可以使用大括号“{}”或者set()函数来创建集合。

我们可以看到下图中，在集合定义的时候，集合中是有重复元素的，但是它自动去除了重复元素：

![图2-61](blob:https://minghuiwu.gitbook.io/8a62ead7-9676-44d0-8e03-418a0aba84eb)

我们也可以使用“in”来判断元素是否在集合中：

![图2-62](blob:https://minghuiwu.gitbook.io/7828efa7-852b-4743-8ecd-e2ed5db1a2e2)

集合也有许多的操作：交（&）、并（|）、差（-）、补（^）

![图2-63](blob:https://minghuiwu.gitbook.io/1050965a-0f88-4e53-a463-39e2fe71c912)

![图2-64](blob:https://minghuiwu.gitbook.io/2d634bba-2aa3-4833-9f5c-b14d7bc38f8c)

集合的补也可以用两个集合的并集减去两个集合的交集得到。


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