set 是一个无序不重复的元素集，集合跟字典是无序的，不支持索引

创建集合：

第一种方式：通过{ }创建

>>> num={1,2,3,4,3,3,1}>>> num{
    1, 2, 3, 4}>>> type(num)
     

第二种方式：通过set() 

>>> li=set(['aaa','bbb','aaa'])>>> li{
    'aaa', 'bbb'}

 

可以去除列表里的重复项但不能保证顺序：

>>> num=[4,3,2,1,2,2]

>>> num=list(set(num))

>>> num

[1, 2, 3, 4]

 

class set(object):    def add(self, *args, **kwargs): #添加,把传入的元素作为一个整个添加进去        >>> st.add('python')        >>> st        {
    'd', 'f', 'python', 'a', 'b', 'c'}            def update(self, *args, **kwargs): # 更新，把传入的元素拆分然后传入集合        """         >>> s1=set('boy')        >>> s1        {'b', 'y', 'o'}        >>> s1.update('python')        >>> s1        {'t', 'y', 'p', 'n', 'h', 'b', 'o'}        """        pass    def clear(self, *args, **kwargs): # 清空        >>> st.clear()        >>> st        set()        pass    def copy(self, *args, **kwargs): # 拷贝    def difference(self, *args, **kwargs): #差集。在s1集合,不在s2集合的,操作后可以输出返回值        >>> s1=set(['aaa','bbb'])        >>> s2=set(['bbb','ccc'])        >>> s1.difference(s2)        {
    'aaa'}    def difference_update(self, *args, **kwargs): #将s1更新为s1-s2的差集。没有返回值        >>> s1         {
    'aaa', 'bbb'}        >>> s2         {
    'bbb', 'ccc'}        >>> s1.difference_update(s2)        >>> s1         {
    'aaa'}        >>> s2         {
    'bbb', 'ccc'}    def discard(self, *args, **kwargs):  # 删除             def remove(self, *args, **kwargs): # 删除     #set.remove(obj)和set.discard(obj)的区别在于，当obj存在于set中时，都将其删除；但当obj不存在于set中时，remove()会报错，discard()不会。    def pop(self, *args, **kwargs): # 随机删除        >>> a=set('abcd')        >>> a.pop()        'b'        >>> a.pop()        'd'    def intersection(self, *args, **kwargs): # 交集 s1 & s2        >>> s1=set(['aaa','bbb'])        >>> s2=set(['bbb','ccc'])        >>> d=s1.intersection(s2)        >>> print(d)         {
    'bbb'}    def intersection_update(self, *args, **kwargs): # 交集 s1更新为这个值        def isdisjoint(self, *args, **kwargs): # 没有交集       >>> s1.isdisjoint(s2)       False     def issubset(self, *args, **kwargs): #  s1的每一个元素都在s2中       >>> s1=set('abc')       >>> s2=set('abcdef')       >>> s1.issubset(s2)       True    def issuperset(self, *args, **kwargs):  # s2的每一个元素都在s1中        >>> s1.issuperset(s2)       False    def symmetric_difference(self, *args, **kwargs): # s1,s2的对称差，有返回值        >>> s1=set(['aaa','bbb'])        >>> s2=set(['bbb','ccc'])        >>> d=s1.symmetric_difference(s2)        >>> print(d)         {
    'ccc', 'aaa'}    def symmetric_difference_update(self, *args, **kwargs): # s1更新为s1,s2的对称差，没有返回值        >>> s1=set(['aaa','bbb'])        >>> s2=set(['bbb','ccc'])        >>> s1.symmetric_difference_update(s2)        >>> s1         {
    'aaa', 'ccc'}    def union(self, *args, **kwargs): # 并集  s1 | s2

 

还有一种不可变的集合：frozenset

>>> s = frozenset([1,2,3,4])

>>> s.add(0)

Traceback (most recent call last):

File "<stdin>", line 1, in <module>

AttributeError: 'frozenset' object has no attribute 'add'