【5.4】set和frozenset

#!/user/bin/env python
# -*- coding:utf-8 -*-
# set集合 frozenset不可变集合， 无序、不重复
# set()函数接收一个可迭代对象
# s = set('abcdefa')
s = {'a', 'b'}
s.add('c')
print(s)

# frozenset不可变集合,可以作为dict的key
fs = frozenset('abcd')
print(fs)

# 向set添加数据
another_set = set('def')
s.update(another_set)
print(s)

# difference,返回一个新的set s - another_set
re_set = s.difference(another_set)
print(re_set)
re_set = s - another_set
print(re_set)
# 交集
re_set = s & another_set
print(re_set)
# 并集
re_set = s | another_set
print(re_set)

# 实现__contains__魔法函数
if 'a' in s:
    print('i am in set')

# issubset判断是不是子集
a = {'a', 'b'}
b = {'a'}
re = b.issubset(a)
print(re)

{'b', 'a', 'c'}
frozenset({'b', 'a', 'd', 'c'})
{'c', 'a', 'f', 'b', 'e', 'd'}
{'c', 'a', 'b'}
{'c', 'a', 'b'}
{'e', 'd', 'f'}
{'b', 'f', 'c', 'a', 'e', 'd'}
i am in set
True