python set 集合

set 集合 无序 不可重复 可以用来过滤元素

语法 set= (,,) 当set集合只有一个数值是，数值后加，号
定义空的set集合 set1=set()

集合.add(va) 把va添加到set集合中 单个元素的增加用add方法，

    set1 = {1,2,3,4,5,6}
    set1.add(10)
    print(set1)

集合.remove(va) 把va从集合中删除

    set1 = {1,2,3,4,5,6}
    set1.remove(2)
    print(set1)

| 并集

    set1 = {1,2,3,4,5,6}
    set2 = {3,4,5,6,7,8}
    ret = set1 | set2
    print(ret)

& 交集

    set1 = {1,2,3,4,5,6}
    set2 = {3,4,5,6,7,8}
    ret = set1 & set2
    print(ret)

- 差集

    set1 = {1,2,3,4,5,6}
    set2 = {3,4,5,6,7,8}
    ret = set1 - set2
    ret1 = set2-set1
    print(ret)
    print (ret1)

对序列的增加用update方法

    # 集合.update(x) 把x中的内容并入到前一个集合中，x可以是列表，集合
    set1 = {1,2,}
    print(type(set1))
    x= {1:2,2:3}
    set1.update(x)
    print(set1)

    #集合.discard(x)  把x从集合中移除
    set1 = {1,2,3,4,5,6}
    x=3
    set1.discard(x)
    print(set1)

    #集合.pop() 随机删除集中的值，并返回
    set1 = {7,2,3,4,5,6}
    ret=set1.pop()
    print(set1)
    print(ret)

    # 集合.clear() 清空集合
    set1 = {7,2,3,4,5,6}
    set1.clear()
    print(set1)

    # in  判断值是否在集合中
    set1 = {7,2,3,4,5,6}
    print(7 in set1)


    set1 = {7,2,3,4,5,6}
    x=[1,2,3,4,]
    ret=set1.union(x)   # 集合.union(x) 返回集合 与x 的交集
    ret1=set1.intersection(x)  # 集合.intersection(x) 返回集合 与x 的并集
    ret3 = set1.difference(x)  # 集合1.difference(x)  返回值在集合1而不再x中的值
    print (ret)
    print (ret1)
    print (ret3)

    set1 = {7,2,3,4,5,6}
    x=[1,2,3,4,]
    #  集合1.symmetric_difference(x)  返回只在集合1或x中的值
    ret=set1.symmetric_difference(x)
    print(ret)

    # 集合.issubset(x)判断集合是不是x的子集
    set1 = {7,2,3,4,5,6}
    x=[1,2,3,4,]
    y={2,3}
    print(set1.issubset(x))
    print(y.issubset(set1))
    #  集合.issuperset(x)判断x是不是集合的子集
    print(set1.issuperset(x))