python基础数据类型（四）集合

1.集合dict

集合是无序的，不重复的数据集合，它里面的元素是可哈希的(不可变类型)，但是集合本身是不可哈希（所以集合做不了字典的键）的。以下是集合最重要的两点：
　　去重，把一个列表变成集合，就自动去重了。
　　关系测试，测试两组数据之前的交集、差集、并集等关系。

2.创建

# #创建
# #one
set1 = set({1,2,3,'哈哈','呵呵'})
print(set1)

# #two
set2 = {1,2,3,'哈哈','呵呵'}
print(set2)

3.增加

#增
#one add
set1 = set({1,2,3,'哈哈','呵呵'})
set1.add('嘿嘿')
print(set1)

#two update
set1 = set({1,2,3,'哈哈','呵呵'})
set1.update('今天是个好日子')
print(set1)

4.删除

#删除
set1 = set({1,2,3,'哈哈','呵呵'})
#pop
set1.pop()  #随机删除一个元素
print(set1)

#remove
set1 = set({1,2,3,'哈哈','呵呵'})
set1.remove(1) #按元素删除
print(set1)

#clear
set1 = set({1,2,3,'哈哈','呵呵'})
set1.clear()    #清空
print(set1)

#del
set1 = set({1,2,3,'哈哈','呵呵'})
del set1

5.查看

#查
set1 = set({1,2,3,'哈哈','呵呵'})
for i in set1:
    print(i)

6.交集 &  或者 intersection

set1 = {1,2,3,4,5}
set2 = {4,5,6,7,8}
print(set1 & set2) 
print(set1.intersection(set2)) 

7.并集 | 或者 union

set1 = {1,2,3,4,5}
set2 = {4,5,6,7,8}
print(set1 | set2)  # {1, 2, 3, 4, 5, 6, 7}
print(set2.union(set1))  # {1, 2, 3, 4, 5, 6, 7}

8.差集 - 或者 difference

set1 = {1,2,3,4,5}
set2 = {4,5,6,7,8}
print(set1 - set2)  
print(set1.difference(set2))  

9.反交集 ^ 或者 symmetric_difference

set1 = {1,2,3,4,5}
set2 = {4,5,6,7,8}
print(set1 ^ set2) 
print(set1.symmetric_difference(set2)) 

10.子集与超集

set1 = {1,2,3}
set2 = {1,2,3,4,5,6}

print(set1 < set2)
print(set1.issubset(set2))  
print(set2 > set1)
print(set2.issuperset(set1))