集合定义

集合里面的元素是不可重复的;

s={1,1,2,3,4,2,2}print(s){1, 2, 3, 4}

如何定义一个空集合?

s1 = {} # 默认情况是dict， 称为字典print(s1,type(s1)){} 
    

定义一个空集合

s2 = set([])print(s2,type(s2))set() 
    

集合应用

列表去重

lee =[1,1,23,45,565,4,32,12,23,1]print(list(set(lee)))[32, 1, 4, 12, 45, 565, 23]

集合特性

集合支持的特性只有成员操作符。索引，切片，重复，连接均不支持

s={1,1,2,3,4,2,2}#print(s[0])报错，不支持索引，'set' object does not support indexing#print(s[:])报错，不支持切片，'set' object is not subscriptable#print(s*2)报错，不支持重复，unsupported operand type(s) for *: 'set' and 'int'#print(s+{12,3})，报错，不支持连接，unsupported operand type(s) for +: 'set' and 'set'for item in s:    print(item,end=';')    1;2;3;4;Process finished with exit code 0

集合常用方法

增加元素

• add()

单个元素

s={1,2,3,4}s.add(5)print(s){1, 2, 3, 4, 5}

• update()

多个元素，只能以集合形式添加

s={1,2,3,4}s.update({5,8,0})print(s){0, 1, 2, 3, 4, 5, 8}

删除

• pop()

随机删除一个元素

s={1,2,3,4}s.pop()print(s){2, 3, 4}

• remove()

删除指定元素

s={1,2,3,4}s.remove(3)print(s){1, 2, 4}

交集，并集，差集

• 交集

s1 = {1, 3, 5, 7, 9, 11}s3 = {1, 3, 5, 7, 8, 10, 12}print(s1.intersection(s3))print(s1&s3){1, 3, 5, 7}{1, 3, 5, 7}

• 并集

s1 = {1, 3, 5, 7, 9, 11}s2 = {2, 4, 6, 8, 10, 12}print(s1.union(s2))print(s1 | s2){1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12}{1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12}

• 差集

s1 = {1, 3, 5, 7, 9, 11}s3 = {1, 3, 5, 7, 8, 10, 12}print(s1.difference(s3))    #元素在s1中不在s3中print(s1-s3){9, 11}{9, 11}

对等差分

s1 = {1, 3, 5, 7, 9, 11}s3 = {1, 3, 5, 7, 8, 10, 12}print(s1.symmetric_difference(s3))    #找出两者不一样的元素，两者的并集-交集print(s1^s3){8, 9, 10, 11, 12}{8, 9, 10, 11, 12}