为啥今天又重提这个数据类型呢？平时用的少，等要用起来的时候才发现，自己对这块啥都不知道了，so，今天就把这块再梳理一下咯。
一、set集合，是一个无序且不重复的元素集合。这一点是非常重要的。
二、集合中的方法介绍：
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
集合方法摘录
三、常用方法举例：
linux = set(['alex','jack','rain','sb'])
python = set(['sb','alex','mack','rachel']) #集合linux与集合python 中都有的（交集）
a = linux.intersection(python)
print(a) # {'sb', 'alex'} # 求差集 linux 中有而python中没有的
b = linux.difference(python)
print(b) # {'rain', 'jack'}
集合部分的简单操作也就这些内容了。