集合的定义方式
定义一个空集合 s = set ()
包含一个元素集合 s = {"hello"}
定义多个元素集合 s = {"python","java"}
注意：set中元素不可重复，类似dict中的键，且无序，集合里面不能包含list
集合增、删、查
增：set(add)
- 题目1：set1 = {"python",java } # 则需要增加一个php
set1.add ("php") # 注意增加的位置随机的
- 题目2：set1 = {"python","java"}
set2 = {"jenkins","mysql"}
则需要把set2放到set1里面去
set1.update(set2)输出结果set1就包含set2
删：
- 题目3：set1 = {"python",java } 则删除其中一个元素
set1.pop() # 注意：删除集合中的任意一个元素可能是python也可能是java
set1.remove("java") # 注意：remove删除的是指定元素
set1.discar("python") # 注意：discar删除如果里面有或无"Python"均不会报错，但是remove就会报错
查：
- 题目4：set1 = {"python",java }
len(set1) # 统计集合里面元素个数
其他：
set1.clear() # 清空集合里面内容
- 题目5：set1 = {"python",java }
set2 = set1.copy() # 复制集合这这时候set2也等于{python,java}
六种集合的方法：
交集：&
- 题目6：code = {"python",java }
code1 = {"python","php","java"}
code & code1 也可以code.intersection(code1),code&code1 # 则输出结果就是python,java,php
并集：|
- 题目7：code = {"python","java","js" }
code1 = {"python","php","java"}
code | cpde1 也可以code.union(code1),code|code1 # 则输出结果就是python,java,php,js
差集：-
- 题目8：code = {"python","java","js" }
code1 = {"python","php","java"}
code - code1 也可以code.difference,code-code1 # 则输出结果就是js,php
对称差集：^
- 题目9：code = {"python","java","js" }
code1 = {"python","php","java"}
code ^ code1 也可以写成code.symmetric_difference # 则输出就是js,php (意思就是输出code,code1两个不一样的元素)
子集：<=
- 题目10：code = {"python","java",20，30 }
code1 = {"python"}
code1 <= code 也可以写成code1.issubset(code) # 则输出就是True(意思是code1是code元素里面的一个子集)
包含：>=
- 题目11：code = {"python","java",20，30 }
code1 = {"python"}
code >= code1 也可以写成code.issuperset(code1) # 则输出就是True(意思是code包含code1元素)
四种集合赋值方法：
交集并赋值： &=
- 题目12：set1 = {"php","java",2018}
set2 = {"java","2019","python"}
set1 &= set2 也可以写成set1.intersection_update(set2) # 则输出就是python(注意这时候set1赋值后是python，而不是php,java,2018)
并集并赋值： |=
- 题目13：set1 = {"php","java",2018}
set2 = {"java","2019","python"}
set1 |= set2 也可以写成set1.update(set2) # 则输出结果就是python,java,php,2019,2018
差集并赋值： -=
- 题目14：set1 = {"php","java",2018}
set2 = {"java","2019","python"}
set1 -= set2 也可以写成set1.difference_update(set2) # 则输出结果就是2018，php
对称集并赋值：^=
- 题目15：set1 = {"php","java",2018}
set2 = {"java","2019","python"}
set1^= set2 也可以写成set1.symmetrin_update # 则输出结果是2018，2019，php,java (对称集就是去除所重复的数据)