Python的set集合浅析

set是一个无序且不重复的元素集合

set的优点：访问速度快；天生解决重复问题

部分源码分析如下：

def add(self, *args, **kwargs): # real signature unknown
        """
        Add an element to a set.
        
        This has no effect if the element is already present.
        """
        pass

#练习1.添加
s1 = set()
s1.add("11,22,33")    #可以添加字符串和元组，不能添加列表，字典，每次只能添加一个
s1.add("kkkkkkkk")
print(s1)
s1.add("11,22,33")      #添加重复字符串不生效
s1.add(("k1","v1"))
print(s1)

#执行结果：
{'11,22,33', 'kkkkkkkk'}
{'11,22,33', 'kkkkkkkk', ('k1', 'v1')}
注意：另外一种方法可以添加列表，字典

s2 = set([44,55,66,"aaa"])     #感觉像是赋值，因为后面被覆盖了
print(s2)
s2 = set({"kk":"vv","jj":"oo"})    #如果是字典取key
print(s2)

执行结果：
{66, 'aaa', 44, 55}
{'kk', 'jj'}

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

#练习2.清空set集合
s1 = set()
s1.add("11,22,33")    #可以添加字符串和元组，不能添加列表，字典，每次只能添加一个
print(s1)
s1.clear()     #清空set集合了
print(s1)   

#执行结果：
{'11,22,33'}
set()

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

#练习3.比较不同的部分放到新集合
s2 = set(["aaa","bbb","ccc","ddd","aaa"])
print(s2)
ret = s2.difference(["aaa","bbb","kkk"])    #输出与指定集合不相同的部分放到新集合，无序
print(ret)

执行结果：
{'aaa', 'ddd', 'bbb', 'ccc'}
{'ccc', 'ddd'}

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

#练习4.更新原有集合，移除相同部分
s2 = set(["aaa","bbb","ccc","ddd","aaa"])
print(s2)
ret = s2.difference_update(["aaa","bbb"])    #更新原来的集合,移除相同部分，不生成集合
print(s2)
print(ret)      #不生成新集合，所以返回了None

#执行结果：
{'ddd', 'bbb', 'ccc', 'aaa'}
{'ccc', 'ddd'}
None

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

#练习5.移除集合里的单个元素
s2 = set(["aaa","bbb","ccc","ddd"])
print(s2)
s2.discard("aaa")     #移除一个元素，如果元素不存在，do nothing
print(s2)

#执行结果：
{'aaa', 'ccc', 'bbb', 'ddd'}
{'ccc', 'bbb', 'ddd'}

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

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

#练习6.取交集
s2 = set(["aaa","bbb","ccc","ddd"])
print(s2)
s3 = s2.intersection(["aaa"])     #原集合不变，取交集，并生成新集合
print(s3)
s2.intersection_update(["aaa"])    #更新原集合，移除原集合内容，放进交集
print(s2)

执行结果：
{'ddd', 'bbb', 'ccc', 'aaa'}
{'aaa'}
{'aaa'}

def isdisjoint(self, *args, **kwargs): # real signature unknown
        """ Return True if two sets have a null intersection. """
        pass

#练习6.判断是否有交集
s2 = set(["aaa","bbb","ccc","ddd"])
s3 = s2.isdisjoint(["aaa"])     #有交集则返回False
s4 = s2.isdisjoint(["kkk"])     #没交集则返回True
print(s3)
print(s4)

#执行结果：
False
True

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

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

#练习7.判断父子集
s2 = set(["aaa","bbb","ccc","ddd"])
s3 = s2.issubset(["aaa"])     #判断这个集合是否包含原集合，即判断原集合是否子集
s4 = s2.issuperset(["aaa"])     #判断原集合是否包含这个集合，即判断原集合是否父集
print(s3)
print(s4)

#执行结果：
False
True

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

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

#练习8.随机删除和指定删除
s2 = set(["aaa", "bbb", "ccc", "ddd"])
s3 = s2.pop()  # 随机删除集合中的一个元素
print(s2)
s2 = set(["aaa", "bbb", "ccc", "ddd"])
s4 = s2.remove("aaa")  # 指定删除集合中的一个元素
print(s2)

#执行结果：
{'ccc', 'ddd', 'aaa'}
{'bbb', 'ccc', 'ddd'}

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

#练习9.差集
s2 = set(["aaa", "bbb", "ccc", "ddd"])
s3 = s2.symmetric_difference(["aaa","kkk"])  # 差集，并生成新集合，与difference区别是，循环多了一次，因此差集最好与交集混合用
print(s3)
s4 = s2.symmetric_difference_update(["bbb"])  # 差集，在原集合中改变
print(s2)

#执行结果：
{'ccc', 'bbb', 'ddd','kkk'}
{'aaa', 'ccc', 'ddd'}

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

#练习10.并集和更新
s2 = set(["aaa", "bbb", "ccc", "ddd"])
s3 = s2.union(["aaa","kkk"])  # 并集，并生成新集合
print(s3)
s4 = s2.update(["bbb","jjj"])  # 更新，在原集合中改变
print(s2)

#执行结果：
{'ccc', 'aaa', 'bbb', 'ddd', 'kkk'}
{'ccc', 'aaa', 'bbb', 'ddd', 'jjj'}