set
创建空集合 a=set()
转化一个数据为集合：set（obj）, 注意数字不能直接转化成集合，其他都可以，只要是可迭代类型
set（一个字典），则集合内元素为字典的键值：
关键是集合内置了去重，交集，并集，差集，对称差集函数，这是别的数据类型没有的
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.) """ passdef 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 """ passdef 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.) """ passdef 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 """ passdef 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 """ passdef 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 """ passdef symmetric_difference(self, *args, **kwargs): # real signature unknown """ Return the symmetric difference of two sets as a new set. 对称差集，所有差集，A中有B中没有+B中有A中没 i.e. all elements that are in exactly one of the sets.) """ passdef 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 """ passdef 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.) """ passdef update(self, *args, **kwargs): # real signature unknown """ Update a set with the union of itself and others. 更新 """ pass实例：
