python入门到放弃(八)-基本数据类型之set集合

1.概述

集合：python中的一个基本数据类型

set集合中的元素是不可以重复的，无序的，里面的元素必须是可hash，不可变的数据类型(int,int,bool,tuple)

set集合就是不保存值的字典，如{'张三','李四'}

set集合本身就是可变的数据类型

#扩展：可变和不可变数据类型

#可变数据类型：当该数据类型的对应变量的值发生了改变，那么它对应的内存地址不发生改变
#例子：
lst1 = [1,2,3,True]
print(id(lst1))
lst1.append(False)
print(id(lst1))
# 1695428338184
# 1695428338184

#不可变的数据类型：当数据类型对应的变量的值发生改变，变量的内存地址也发生了改变
#例子：
a = 1
print(id(a),type(a))
a = 2
print(id(a),type(a))
#140704654406480 <class 'int'>
# 140704654406512 <class 'int'>

#先来看看set集合的源码写了什么，方法:按ctrl+鼠标左键点set

class set(object):
    """
    set() -> new empty set object
    set(iterable) -> new set object
    
    Build an unordered collection of unique elements.
    """
    def add(self, *args, **kwargs): # real signature unknown
        """ 添加 """
        """
        Add an element to a set.
        
        This has no effect if the element is already present.
        """
        pass

    def clear(self, *args, **kwargs): # real signature unknown
        """ Remove all elements from this set. """
        pass

    def copy(self, *args, **kwargs): # real signature unknown
        """ Return a shallow copy of a set. """
        pass

    def difference(self, *args, **kwargs): # real signature unknown
        """
        Return the difference of two or more sets as a new set.
        
        (i.e. all elements that are in this set but not the others.)
        """
        pass

    def difference_update(self, *args, **kwargs): # real signature unknown
        """ 删除当前set中的所有包含在 new set 里的元素 """
        """ Remove all elements of another set from this set. """
        pass

    def discard(self, *args, **kwargs): # real signature unknown
        """ 移除元素 """
        """
        Remove an element from a set if it is a member.
        
        If the element is not a member, do nothing.
        """
        pass

    def intersection(self, *args, **kwargs): # real signature unknown
        """ 取交集，新创建一个set """
        """
        Return the intersection of two or more sets as a new set.
        
        (i.e. elements that are common to all of the sets.)
        """
        pass

    def intersection_update(self, *args, **kwargs): # real signature unknown
        """ 取交集，修改原来set """
        """ Update a set with the intersection of itself and another. """
        pass

    def isdisjoint(self, *args, **kwargs): # real signature unknown
        """ 如果没有交集，返回true  """
        """ Return True if two sets have a null intersection. """
        pass

    def issubset(self, *args, **kwargs): # real signature unknown
        """ 是否是子集 """
        """ Report whether another set contains this set. """
        pass

    def issuperset(self, *args, **kwargs): # real signature unknown
        """ 是否是父集 """
        """ Report whether this set contains another set. """
        pass

    def pop(self, *args, **kwargs): # real signature unknown
        """ 移除 """
        """
        Remove and return an arbitrary set element.
        Raises KeyError if the set is empty.
        """
        pass

    def remove(self, *args, **kwargs): # real signature unknown
        """ 移除 """
        """
        Remove an element from a set; it must be a member.
        
        If the element is not a member, raise a KeyError.
        """
        pass

    def symmetric_difference(self, *args, **kwargs): # real signature unknown
        """ 差集，创建新对象"""
        """
        Return the symmetric difference of two sets as a new set.
        
        (i.e. all elements that are in exactly one of the sets.)
        """
        pass

    def symmetric_difference_update(self, *args, **kwargs): # real signature unknown
        """ 差集，改变原来 """
        """ Update a set with the symmetric difference of itself and another. """
        pass

    def union(self, *args, **kwargs): # real signature unknown
        """ 并集 """
        """
        Return the union of sets as a new set.
        
        (i.e. all elements that are in either set.)
        """
        pass

    def update(self, *args, **kwargs): # real signature unknown
        """ 更新 """
        """ Update a set with the union of itself and others. """
        pass

    def __and__(self, y): # real signature unknown; restored from __doc__
        """ x.__and__(y) <==> x&y """
        pass

    def __cmp__(self, y): # real signature unknown; restored from __doc__
        """ x.__cmp__(y) <==> cmp(x,y) """
        pass

    def __contains__(self, y): # real signature unknown; restored from __doc__
        """ x.__contains__(y) <==> y in x. """
        pass

    def __eq__(self, y): # real signature unknown; restored from __doc__
        """ x.__eq__(y) <==> x==y """
        pass

    def __getattribute__(self, name): # real signature unknown; restored from __doc__
        """ x.__getattribute__('name') <==> x.name """
        pass

    def __ge__(self, y): # real signature unknown; restored from __doc__
        """ x.__ge__(y) <==> x>=y """
        pass

    def __gt__(self, y): # real signature unknown; restored from __doc__
        """ x.__gt__(y) <==> x>y """
        pass

    def __iand__(self, y): # real signature unknown; restored from __doc__
        """ x.__iand__(y) <==> x&=y """
        pass

    def __init__(self, seq=()): # known special case of set.__init__
        """
        set() -> new empty set object
        set(iterable) -> new set object
        
        Build an unordered collection of unique elements.
        # (copied from class doc)
        """
        pass

    def __ior__(self, y): # real signature unknown; restored from __doc__
        """ x.__ior__(y) <==> x|=y """
        pass

    def __isub__(self, y): # real signature unknown; restored from __doc__
        """ x.__isub__(y) <==> x-=y """
        pass

    def __iter__(self): # real signature unknown; restored from __doc__
        """ x.__iter__() <==> iter(x) """
        pass

    def __ixor__(self, y): # real signature unknown; restored from __doc__
        """ x.__ixor__(y) <==> x^=y """
        pass

    def __len__(self): # real signature unknown; restored from __doc__
        """ x.__len__() <==> len(x) """
        pass

    def __le__(self, y): # real signature unknown; restored from __doc__
        """ x.__le__(y) <==> x<=y """
        pass

    def __lt__(self, y): # real signature unknown; restored from __doc__
        """ x.__lt__(y) <==> x<y """
        pass

    @staticmethod # known case of __new__
    def __new__(S, *more): # real signature unknown; restored from __doc__
        """ T.__new__(S, ...) -> a new object with type S, a subtype of T """
        pass

    def __ne__(self, y): # real signature unknown; restored from __doc__
        """ x.__ne__(y) <==> x!=y """
        pass

    def __or__(self, y): # real signature unknown; restored from __doc__
        """ x.__or__(y) <==> x|y """
        pass

    def __rand__(self, y): # real signature unknown; restored from __doc__
        """ x.__rand__(y) <==> y&x """
        pass

    def __reduce__(self, *args, **kwargs): # real signature unknown
        """ Return state information for pickling. """
        pass

    def __repr__(self): # real signature unknown; restored from __doc__
        """ x.__repr__() <==> repr(x) """
        pass

    def __ror__(self, y): # real signature unknown; restored from __doc__
        """ x.__ror__(y) <==> y|x """
        pass

    def __rsub__(self, y): # real signature unknown; restored from __doc__
        """ x.__rsub__(y) <==> y-x """
        pass

    def __rxor__(self, y): # real signature unknown; restored from __doc__
        """ x.__rxor__(y) <==> y^x """
        pass

    def __sizeof__(self): # real signature unknown; restored from __doc__
        """ S.__sizeof__() -> size of S in memory, in bytes """
        pass

    def __sub__(self, y): # real signature unknown; restored from __doc__
        """ x.__sub__(y) <==> x-y """
        pass

    def __xor__(self, y): # real signature unknown; restored from __doc__
        """ x.__xor__(y) <==> x^y """
        pass

    __hash__ = None

set

#集合里面的元素必须可hash的，不可变的数据类型

#例子：如果使用可变数据类型，不可哈希的元素就会报错
#提示：不可变的数据类型：int,bool,str,tuple,可变的数据类型有：list,dict,set
# set1 = {'1','sir',2,True,[1,2,3]} #报错，有列表，
# set2 = {'1','sir',2,{"a":2}} #报错，有字典
# set3 = {'1','sir',{'1','sir'}} #报错，有集合

#集合的常用例子(去重)

#set集合中的元素是不重复的，且无序的
a = {"蒋小雨","鲁炎","张冲","鲁炎"}
print(a)
#{'蒋小雨', '张冲', '鲁炎'}:会去掉重复的，且不按顺序排

#####set集合最常用的就是去重###
a = [1,3,4,4,3,2,3,4,5,5,5,45,5,254,54]
s = set(a) #把列表转换成集合，进行去重复
lst = list(s) #把集合转换回列表
print(lst) #[1, 2, 3, 4, 5, 45, 54, 254]
# 或者
print(list(set(a))) #[1, 2, 3, 4, 5, 45, 54, 254]

2.集合的增删改查

#注意点1：集合中的元素是不重复的，且无序的，所以打印出来的元素位置可能会和定义的位置不一样

#注意点2：set集合是本身可变的数据类型，所以可以直接在原来的对象上进行操作

#2.1.增加

#关键字
#1.add
#2.update(迭代更新)

#例子：

s = {"蒋小鱼","鲁炎","张冲"}
s.add("龙大队")
print(s) #{'蒋小鱼', '龙大队', '鲁炎', '张冲'}
s.add("龙大队")  #如果重复的内容是不会被添加进去的
print(s) #{'蒋小鱼', '龙大队', '鲁炎', '张冲'}

s = {"蒋小鱼","鲁炎","张冲"}
s.update("武黑脸")  #迭代更新，一个字一个字添加
print(s) #{'蒋小鱼', '鲁炎', '脸', '张冲', '武', '黑'}

#2.2.删除

#关键字：
#1.pop()     #随机删除
#2.remove(n) #指定元素删除
#3.clear()   #清空 

#例子：

s = {"蒋小鱼","鲁炎","张冲","阿甘"}
item = s.pop() #随机删除
print(s) #{'张冲', '鲁炎', '阿甘'}
print(item) #蒋小鱼 ：查看到被删除的是蒋小鱼

s.remove("张冲") #直接删除指定的元素
# s.remove("黑脸")  #如果删除不存在的元素就会报错
print(s) #{'蒋小鱼', '鲁炎', '阿甘'}

s.clear() #情况set集合，需要注意的是set集合如果是空的，打印出来的是set(),因为要和dict区分的
print(s) #set()

#2.3.修改

#set集合中的数据没有索引，因为是无序的，所有没有办法去定位一个元素，所以没办法直接修改
# 但是可以采用先删除后添加的方式来完成修改操作

#例子：

s = {"蒋小鱼","鲁炎","张冲","阿甘"}
s.remove("鲁炎")
s.add("龙大队")
print(s) #{'阿甘', '蒋小鱼', '龙大队', '张冲'}

#2.4.查询

#set是一个可迭代对象，所以可以进行for循环
s = {"蒋小鱼","鲁炎","张冲","阿甘"}
for el in s:
    print(el)

3.集合的常用操作

常用操作有:交集，并集，差集，反交集，子集，超集

#例子:

a1 = {"蒋小鱼","鲁炎","张冲","阿甘"}
a2 = {"刘能","赵四","张冲","谢大脚"}

#3.1.交集：就是两个集合中的共有元素

print(a1 & a2) #{'张冲'}
#或者
print(a1.intersection(a2)) #{'张冲'}

#3.2.并集：蒋两个集合合并起来

print(a1 | a2) #{'张冲', '鲁炎', '阿甘', '赵四', '刘能', '蒋小鱼', '谢大脚'}
print(a1.union(a2)) #{'张冲', '鲁炎', '阿甘', '赵四', '刘能', '蒋小鱼', '谢大脚'}

#3.3.差集：得到某一个中单独存在的

print(a1 - a2) #{'鲁炎', '阿甘', '蒋小鱼'} :得到第一个中单独存在的，如果是a2-a1,那么得到的是第二个中单独存在的
print(a1.difference(a2)) #{'蒋小鱼', '阿甘', '鲁炎'}

#3.4.反交集:得到两个集合中单独存在的数据，就是两个不一样的

print(a1 ^ a2)
# #{'谢大脚', '蒋小鱼', '赵四', '刘能', '鲁炎', '阿甘'}
print(a1.symmetric_difference(a2))

#3.5.子集: 谁是谁的子集,简单说就是你有的别人也有，别人有的你没有

a1 = {"蒋小鱼","张冲"}
a2 = {"蒋小鱼","张冲","谢大脚"}

print(a1 < a2) #a1是a2的子集吗？ #True
print(a1.issubset(a2)) #True

#3.6.超集：如果一个集合a1中的每一个元素都在集合a2中，且集合a2中可能包含a1中没有的元素，则集合a2就是a1的一个超集。

a1 = {"蒋小鱼","张冲"}
a2 = {"蒋小鱼","张冲","谢大脚"}
print(a1 > a2) #False #a1是a2的超集吗
print(a1.issuperset(a2)) #Flase