python中set集合

一、set集合的特性

1. 访问速度快
2. 天生解决重复问题

二、set变量申明

1. s1 = set()
2. s2 = set([1,2,3])

备注：第二种方式在set类中直接传入一个序列。

三、set类中方法大全

1.add函数：

 def add(self, *args, **kwargs): # real signature unknown
         '''--向一个set集合中添加一个元素--'''
         """
         Add an element to a set.

         This has no effect if the element is already present.
         """

add

例:

>>> s1 = set()
>>> s1.add(1)
>>> s1
{1}

2.clear函数：

 def clear(self, *args, **kwargs): # real signature unknown
         '''--清除set集合中的所有元素--'''
         """ Remove all elements from this set. """
         pass

clear

例：

>>> s1 = set([1,2,3])
>>> s1
{1, 2, 3}
>>> s1.clear()
>>> s1
set()

3.copy函数：

 def copy(self, *args, **kwargs): # real signature unknown
        '''--返回一个浅拷贝的set集合--'''
         """ Return a shallow copy of a set. """
         pass

copy

例：

pass

4.difference函数：

 def difference(self, *args, **kwargs): # real signature unknown
          '''--比较两个set集合得到一个差集--'''
          """
          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

difference

例：

>>> s1 = set(['one','two','three'])
>>> s2 = s1.difference(['one','two'])
>>> s2
{'three'}

 5.difference_update函数：

 def difference_update(self, *args, **kwargs): # real signature unknown
         '''-新set集合与原来set相比较，从原来set集合中删除新set集合中存在的元素-'''
         """ Remove all elements of another set from this set. """
         pass    

difference_update

例：

>>> s1 = set(['one','two','three'])
>>> s1.difference_update(['one','three'])
>>> s1
{'two'}

6.discard函数：

 def discard(self, *args, **kwargs): # real signature unknown
         '''-指定删除set集合中的某个元素,如果指定元素不在set集合中，则返回一个none-'''
         """
         Remove an element from a set if it is a member.

         If the element is not a member, do nothing.
         """
         pass    

discard

例：

①指定元素存在set集合中：

>>> s1 = set(['one','two','three'])
>>> s1.discard('one')
>>> s1
{'three', 'two'}

②指定元素不存在集合中：

>>> s1 = set(['one','two','three'])
>>> a=s1.discard('four')
>>> print(a)
None

7.intersection函数：

 def intersection(self, *args, **kwargs): # real signature unknown
         '''--返回两个set集合交集--'''
         """
         Return the intersection of two sets as a new set.

         (i.e. all elements that are in both sets.)
         """
         pass

intersection

例：

>>> s1 = set(['one','two','three'])
>>> s2 = set(['one','three'])
>>> s3 = s1.intersection(s2)
>>> s3
{'one', 'three'}

8.intersection_update函数：

 def intersection_update(self, *args, **kwargs): # real signature unknown
         '''--将老set集合的值更新为新set集合与老set集合交集--''
         """ Update a set with the intersection of itself and another. """
         pass

intersection_update

例：

>>> s1 = set(['one','two','three'])
>>> s2 = set(['one','three'])
>>> s1.intersection_update(s2)
>>> s1
{'one', 'three'}

9.isdisjoint函数：

 def isdisjoint(self, *args, **kwargs): # real signature unknown
         '''--如果两个set集合没有交集，返回True--'''
         """ Return True if two sets have a null intersection. """
         pass

isdisjoint

例：

①没有交集：

>>> s1 = set(['one','two','three'])
>>> s2 = set([1,2,3])
>>> s1.isdisjoint(s2)
True

②有交集：

>>> s1 = set(['one','two','three'])
>>> s2 = set(['one'])
>>> s1.isdisjoint(s2)
False

 10.issubset函数：

 def issubset(self, *args, **kwargs): # real signature unknown
         '''--判断当前这个set集合是否是另一个set集合的子集--'''
         """ Report whether another set contains this set. """
         pass

issubset

例：

>>> s1 = set(['one','two','three'])
>>> s2 = set(['one'])
>>> s2.issubset(s1) #是子集的情况
True
>>> s1.issubset(s2) #不是子集的情况
False

11.issuperset函数：

 def issuperset(self, *args, **kwargs): # real signature unknown
         '''--判断当前这个set集合是否是另外一个set集合父集--'''
         """ Report whether this set contains another set. """
         pass

issuperset

例：

>>> s1 = set(['one','two','three'])
>>> s2 = set(['one'])
>>> s1.issuperset(s2)  #s1是s2的父集情况
True
>>> s2.issuperset(s1)  #s2不是s1父集的情况
False

12.pop函数：

 def pop(self, *args, **kwargs): # real signature unknown
         '''--随机删除set集合中的元素，并且返回被删除的元素--'''
         """
         Remove and return an arbitrary set element.
         Raises KeyError if the set is empty.
         """
         pass

pop

例：

>>> s1 = set(['one','two','three'])
>>> s1.pop()
'one'
>>> s1
{'three', 'two'}

13.remove函数：

def remove(self, *args, **kwargs): # real signature unknown
        '''--指定删除set集合中的元素--'''
        """
        Remove an element from a set; it must be a member.

        If the element is not a member, raise a KeyError.
        """
        pass

remove

例：

>>> s1 = set(['one','two','three'])
>>> s1.remove("one")
>>> s1
{'three', 'two'}

14.symmetric_difference函数：

def symmetric_difference(self, *args, **kwargs): # real signature unknown
       '''--两个set集合的对称集--'''
        """
        Return the symmetric difference of two sets as a new set.

        (i.e. all elements that are in exactly one of the sets.)
        """
        pass

symmetric_difference

例：

>>> s1 = set(['one','two','three'])
>>> s2 = set(['one','two','four'])
>>> s3 = s1.symmetric_difference(s2)
>>> print(s3)
{'three', 'four'}

15.symmertric_difference_update函数：

 def symmetric_difference_update(self, *args, **kwargs):
         '''--把两个set集合的交集之外的值，更新替换当前set集合--'''
         """ Update a set with the symmetric difference of itself and another. """
         pass

symmetric_difference_update

例：

>>> s1 = set(['one','two','three'])
>>> s2 = set(['one','two','four'])
>>> s1.symmetric_difference_update(s2)
>>> print(s1)
{'three', 'four'}

16.union函数：

 def union(self, *args, **kwargs): # real signature unknown
         '''--sets集合的并集赋值给一个新的set集合--'''
         """
         Return the union of sets as a new set.

         (i.e. all elements that are in either set.)
         """
         pass

union

例：

>>> s1 = set(['one','two','three'])
>>> s2 = set(['one','two','four'])
>>> s3=s1.union(s2)
>>> print(s3)
{'one', 'three', 'four', 'two'}

 17.update函数：

 def update(self, *args, **kwargs): # real signature unknown
         '''--更新一个set集合，更新的set集合的值是当前集合和其他集合的并集--'''
         """ Update a set with the union of itself and others. """
         pass

update

例：

>>> s1 = set(['one','two','three'])
>>> s2 = set(['one','two','four'])
>>> s1.update(s2)
>>> print(s1)
{'three', 'two', 'four', 'one'}

三、总结

1.函数中有带update的函数，或者本身就是update函数，是更新这个set集合本身，并不会将得到的结果重新赋值给一个变量。

2.函数一些函数不带update的函数，如：difference（取不同），intersection（取交集），symmetric_difference（取交集之外的值），union（取并集）等，将得到的结果返回给一个变量。