6-3 集合set和frozenset

l = ['span','span','eggs','span']

set(l)

{'eggs', 'span'}

set集合是唯一的，同时set集合还实现了交集，合集，差集等运算

m = ['spam','zhou']
mset = set(m)
lset = set(l)

m

['spam', 'zhou']

l

['span', 'span', 'eggs', 'span']

mset

{'spam', 'zhou'}

mset | lset

{'eggs', 'spam', 'span', 'zhou'}

mset & lset

set()

s = frozenset("abcddeeffd")
print(s)
s.add("H")

frozenset({'c', 'd', 'a', 'e', 'f', 'b'})



---------------------------------------------------------------------------

AttributeError                            Traceback (most recent call last)

 in ()
      1 s = frozenset("abcddeeffd")
      2 print(s)
----> 3 s.add("H")


AttributeError: 'frozenset' object has no attribute 'add'

frozenset是不可以修改的