元祖、集合

元组：如果元祖里面只有一个元素且不加逗号，那此元素是什么类型，就是什么类型

tu1 = (1)
tu2 = (1,)
print(tu1,type(tu1))    # 1   <class 'int'>
print(tu2,type(tu2))    #(1,) <class 'tuple'>
tu1 = ([1])
tu2 = ([1],)
print(tu1,type(tu1))    #[1]    <class 'list'>
print(tu2,type(tu2))    #([1],) <class 'tuple'>

集合

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。
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。

①创建集合

set1 = set({123,"ppd"})
set2 = {123,"ppd"}
print(set1,set2)    #{123, 'ppd'} {123, 'ppd'}

②集合的增

set1 = {123,"ppd"}
set1.add("苹果")
print(set1)        {'苹果', 123, 'ppd'}

#update:迭代着增加
set1 = {123, "ppd"}
set1.update("ppd")
print(set1)        #{'ppd', 123, 'p', 'd'}
set1.update("苹果")
print(set1)        {'ppd', 'p', 'd', '苹', 123, '果'}
set1.update([1, 2, 3])
print(set1)        {1, 2, 3, 'ppd', 'p', 'd', '苹', 123, '果'}    

③集合的删

set1 = {123, "ppd", "苹果"}

set1.remove(123)  # 删除一个元素
print(set1)

set1.pop()  # 随机删除一个元素
print(set1)

set1.clear()  # 清空集合
print(set1)  #set()

del set1  # 删除集合
print(set1)  #NameError: name 'set1' is not defined

④集合的查

set1 = {123, "ppd", "苹果"}
for i in set1:
    print(i)

⑤集合的其他运用

交集：&或者intersection

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

反交集：^ 或者symmetric_difference

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

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, 8}
print(set1.union(set2))  # {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)  # {1, 2, 3}    输出set1（set2中有set1的那部分不输出）
print(set1.difference(set2))  #{1, 2, 3}

子集与超集

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

print(set1 < set2)  #set1是set2子集
print(set1.issubset(set2))  # set1是set2子集

print(set2 > set1)  #set2是set1超集
print(set2.issuperset(set1))  # set2是set1超集

frozenset不可变集合，让集合变成不可变类型

s = frozenset("meppd")
print(s, type(s))  #frozenset({'p', 'd', 'e', 'm'}) <class 'frozenset'>