集合：
是由不同元素组成、无序、不可变类型（数字、字符串、元祖）
s = {1，2,3,4，}
>>> s = {1,1,22,22,22,33,33,3,44,44}
>>> type(s)
<class 'set'>
>>> s
{1, 33, 3, 44, 22}
集合可以去重复的，得到的还是随机的，
#求交集：
p_s = set(shudian)
l_s = set(modian)
print(p_s.intersection(l_s))
print(p_s,l_s)
print(p_s&l_s)
#求并集：
#求差集
shudian = ["李强","李程瑞","项羽茂","赵玉伟","sb"]
modian = ["赵玉伟","李强",]
p_s = set(shudian)
l_s = set(modian)
print(p_s-l_s)
print(p_s.difference(l_s))
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.
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. """
pass
def copy(self, *args, **kwargs): # real signature unknown
""" Return a shallow copy of a set. """
pass
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
（求差集， ）def difference_update(self, *args, **kwargs): # real signature unknown
""" Remove all elements of another set from this set. """
pass
def discard(self, *args, **kwargs): # real signature unknown（删除一个数据，不存在不会报错）
"""
Remove an element from a set if it is a member.
If the element is not a member, do nothing.
"""
pass
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
def isdisjoint(self, *args, **kwargs): # real signature unknown
""" Return True if two sets have a null intersection. """
pass
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
def pop(self, *args, **kwargs): # real signature unknown（随机删除）
"""
Remove and return an arbitrary set element.
Raises KeyError if the set is empty.
"""
pass
def remove(self, *args, **kwargs): # real signature unknown（删除，不存在就报错）
"""
Remove an element from a set; it must be a member.
If the element is not a member, raise a KeyError.
"""
pass
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（交叉补集）
""" Update a set with the symmetric difference of itself and another. """
pass
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