Python集合

>>> num = {1, 2, 3, 4, 5, 5, 4, 3, 2, 1}

>>> num

{1, 2, 3, 4, 5}        #集合中所有元素都具有唯一性

創建一個集合

1. 直接把一堆元素用花括號括起來

2. 使用set()工廠函數

>>> num1 = [1, 2, 3, 4, 6, 5, 5, 9, 7,1,7]

>>> num1 = list(set(num1))

>>> num1

[1, 2, 3, 4, 5, 6, 7, 9]

add()    #集合可以使用add添加元素

>>> num1 = {1, 2, 3, 4, 6, }

>>> num1.add(7)

>>> num1

{1, 2, 3, 4, 6, 7}

remove()

>>> num1

{1, 2, 3, 4, 6, 7}

>>> num1.remove(4)

>>> num1

{1, 2, 3, 6, 7}

不可變集合

frozenset()

>>> num2 = frozenset([1,2,3,4,5])

>>> num2.add(9)

Traceback (most recent call last):

  File "<pyshell#83>", line 1, in <module>

    num2.add(9)

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