集合数据类型内置方法

集合数据类型内置方法

一、集合

1.1 作用

存储一大堆元素的东西，容器数据类型

1.2 定义方式

在{}内用逗号分隔不可变数据类型

s = {1, 2, 1, 'a', 'a', 'c'}
print(s)
--------------------------------------------------------
{'c', 1, 2, 'a'}   #去重：重复的全部去掉   #乱序：顺序是乱的

's = {}' #空的大括号是字典，而非集合，定义集合必须要用set()

1.3 内置方法

1.3.1优先掌握

1.长度

s = {1, 2, 1, 'a', 'a', 'c','4'}
print(f"len(s):{len(s)}")

-----------------------------------------------------
len(s):5

2.成员运算in和not in

s = {1, 2, 1, 'a', 'a', 'c','4'}
print(f"1 in s:{1 in s}")
print(f"1 not in s:{1 not in s}")
---------------------------------------------------------
name in dic:False
name not in dic:True

3.|并集union()

s = {1, 2, 1, 'a', 'a', 'c','4'}
s2 = {2,3,3,6,7,8}
print(s | s2)

s = {1,2,1, 'a', 'a', 'c','4'}
s2 = {2,3,3,6,7,8}
s = s.union(s2)
print(s)
------------------------------------------------------
{1, 2, 3, 6, 7, 8, 'c', '4', 'a'}

{1, 2, '4', 3, 6, 7, 8, 'c', 'a'}

4.&交集intersection()

s = {1, 2, 1, 'a', 'a', 'c','4'}
s2 = {2,3,3,6,7,8}
print(s & s2)


s = {1,2,1, 'a', 'a', 'c','4'}
s2 = {2,3,3,6,7,8}
s = s.intersection(s2)
print(s)
---------------------------------------------------------
{2}

{2}

5.-差集difference()

s = {1, 2, 1, 'a', 'a', 'c','4'}
s2 = {2,3,3,6,7,8}
print(s - s2)

s = {1,2,1, 'a', 'a', 'c','4'}
s2 = {2,3,3,6,7,8}
s = s.difference(s2)
print(s)
---------------------------------------------------------
{1, 'a', '4', 'c'}

{1, 'a', 'c', '4'}

6.^对称差集symmetric_difference

s = {1, 2, 1, 'a', 'a', 'c','4'}
s2 = {2,3,3,6,7,8}
print(s ^ s2)


s = {1,2,1, 'a', 'a', 'c','4'}
s2 = {2,3,3,6,7,8}
s = s.symmetric_difference(s2)
print(s)
-----------------------------------------------------------
{1, 3, 6, 7, 8, '4', 'a', 'c'}


{1, 3, 6, 7, 8, '4', 'a', 'c'}

1.3.了解

1.copy()

s = {1, 2, 1, 'a', 'a', 'c','4'}
s.copy()
print(s)
----------------------------------------------------
{'a', 1, 2, '4', 'c'}

2.update()

s = {1, 2, 1, 'a', 'a', 'c','4'}
s2 = {2,3,3,6,7,8}
s.update(s2)
print(s)
{1, 2, 3, 6, 7, 8, 'c', 'a', '4'}

3.clear()

s = {1, 2, 1, 'a', 'a', 'c','4'}
s.clear()
print(s)
---------------------------------------------------------
set()

4.pop()

s = {1, 2, 1, 'a', 'a', 'c','4'}
s.pop()   #随机删除
print(s)
---------------------------------------------------------
{2, 'c', 'a', '4'}

5.remove() :删除

#如果在集合中找不到要删除的元素则会报错
s = {1, 2, 1, 'a', 'a', 'c','4'}
s.remove('a')
print(s)
-----------------------------------------------------------
{1, 2, '4', 'c'}

6.discard()：删除

#如果在集合中找不到要删除的元素则不会会报错
s = {1, 2, 1, 'a', 'a', 'c','4'}
s.discard('a')
print(s)
----------------------------------------------------------
{1, 2, 'c', '4'}

7.add()

s = {1, 2, 1, 'a', 'a', 'c','4'}
s.add(9)
print(s)
---------------------------------------------------------
{1, 2, 9, 'a', 'c', '4'}

8.difference_update()

s = {1,2,1, 'a', 'a', 'c','4'}
s2 = {2,3,3,6,7,8}
s.difference_update(s2)
print(s)
----------------------------------------------------------
{'a', 1, '4', 'c'}

9.子集issubset()

s = {1,2,1, 'a', 'a', 'c','4'}
s2 = {2,3,3,6,7,8}
s = s.issubset(s2)
print(s)
----------------------------------------------------------
False

10.父集

s = {1,2,3, 'a', 'a', 'c','4'}
s2 = {2,3}
s = s.issuperset(s2)
print(s)
---------------------------------------------------------
True

1.4 有一个值还是多个值

多个值

1.5 有序（索引）or无序（索引）

无序

1.6 可变or不可变

可变

s = {1,2}
print(id(s))
s.add(3)
print(id(s))
-------------------------------------------------------------
2199963714952
2199963714952