Python数据结构：集合

s1 = {1,2,3,'a','b','c',7,8,9}
s2 = {}

print(type(s1)) #输出<class 'set'>
print(type(s2)) #输出<class 'dict'>

for i in s1:
    print(i,end=' ') #输出1 2 3 b 7 8 9 a c，可见set是无序的

s1 = {1,2,3}
s2 = {'i', 'love', 'you'}

s3 = {m * n for m in s2 for n in s1} #相当于把s2中的每个元素乘以1/2/3
print(s3) #输出{'iii', 'lovelove', 'you', 'youyou', 'i', 'youyouyou', 'ii', 'love', 'lovelovelove'}

s = {'a','b','c','d','e','f'}
# s.remove('k') #remove删除不存在的元素报错keyerror
s.discard('k') #discard删除不存在的元素不报错，只是删除失败而已

s1 = {1,2,3,4,5,6}
s2 = {5,6,7,8,9,0}

s3 = s1.intersection(s2) #s1与s2的交集
print(s3) #输出{5, 6}

s4 = s1.difference(s2) #s1与s2的差集，相当于s1-s2
print(s4) #输出{1, 2, 3, 4}

s5 = s1.union(s2) #s1与s2的并集
print(s5) #输出{0, 1, 2, 3, 4, 5, 6, 7, 8, 9}

i1 = s1.issubset(s2) #判断s2是否为s1的子集，i1为False
i2 = s1.issuperset(s2) #判断s2是否为s1的超集，i2为False

s = {1,2,3}
s = frozenset(s)
print(s) #输出frozenset({1, 2, 3})