set集合，是一个无序且不重复的元素集合

set集合，是一个无序且不重复的元素集合

 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
         """
         Add an element to a set，添加元素
          
         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. 清除内容"""
         pass
  
     def copy(self, *args, **kwargs): # real signature unknown
         """ Return a shallow copy of a set. 浅拷贝  """
         pass
  
     def difference(self, *args, **kwargs): # real signature unknown
         """
         Return the difference of two or more sets as a new set. A中存在，B中不存在
          
         (i.e. all elements that are in this set but not the others.)
         """
         pass
  
     def difference_update(self, *args, **kwargs): # real signature unknown
         """ Remove all elements of another set from this set.  从当前集合中删除和B中相同的元素"""
         pass
  
     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. 移除指定元素，不存在不保错
         """
         pass
  
     def intersection(self, *args, **kwargs): # real signature unknown
         """
         Return the intersection of two sets as a new set. 交集
          
         (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.  取交集并更更新到A中 """
         pass
  
     def isdisjoint(self, *args, **kwargs): # real signature unknown
         """ Return True if two sets have a null intersection.  如果没有交集，返回True，否则返回False"""
         pass
  
     def issubset(self, *args, **kwargs): # real signature unknown
         """ Report whether another set contains this set.  是否是子序列"""
         pass
  
     def issuperset(self, *args, **kwargs): # real signature unknown
         """ Report whether this set contains another set. 是否是父序列"""
         pass
  
     def pop(self, *args, **kwargs): # real signature unknown
         """
         Remove and return an arbitrary set element.
         Raises KeyError if the set is empty. 移除元素
         """
         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. 移除指定元素，不存在保错
         """
         pass
  
     def symmetric_difference(self, *args, **kwargs): # real signature unknown
         """
         Return the symmetric difference of two sets as a new set.  对称差集
          
         (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. 对称差集，并更新到a中 """
         pass
  
     def union(self, *args, **kwargs): # real signature unknown
         """
         Return the union of sets as a new set.  并集
          
         (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. 更新 """
         pass