Python基础（四）-集合

数据类型总结：

1、按照数据可变不可变：

可变：列表、字典

不可变：数字、字符串、元组

x={'':1}
print(id(x))
x.update({'':2})
print(x)
print(id(x))

#执行结果
5584648
{'': 2, '': 1}
5584648

#列表亦同理
def a(x=[]):
    x.append(1)
    print(id(x))
    return x
print(a())
print(a())

#执行结果
14045576
[1]
14045576
[1, 1]

2、按照访问方式：

直接访问：数字

顺序访问：列表、元组、字符串

映射：字典

3、按照存放元素个数：

容器类型：列表、元组、字典

原子：数字、字符串

bytes类型

定义：存8bit整数，数据基于网络传输或内存变量存储到硬盘时需要转成bytes类型,字符串前置b代表为bytes类型

集合：

特点：无序；元素必须是不可变类型数据；不同元素（无重复元素）

属于可变类

集合创建：

#创建可变集合
a = set()

b=set('hello')
print(b)
# {'o', 'e', 'l', 'h'}

#创建不可变集合
nb = frozenset(b)
print(nb)
frozenset({'l', 'e', 'h', 'o'})

常用方法：

##增

1、add  #一次只能添加一个集合元素

2、update  #增加可迭代数据，把每个元素迭代更新到集合，可以更新多个数据

##删

1、remove()  #删除的元素必须是集合中的元素，否则会报错

2、discard()  #删除的元素可以不是集合中的元素

3、pop()  #随机删除一个元素

4、clear()  #清空

##判断

1、isdisjoint()

判断两个集合是否有交集，没有则返回 True

2、issubset()

a.issubset(b) 判断a 是否是b的子集，是则返回 True

3、issuperset()

a.issuperset() 判断a是否是b的父集合，是则返回 True

##浅复制

1、copy()

##运算

1、交集 & intersection

a.intersection(b)  #a和b相同元素

2、并集 ^ union

a.union(b)  #a和b组成新的集合

3、差集 - difference

a.difference(b)  #存在a中，但不存在b中

4、symmetric_difference #对称差

a.symmetric_difference(b)== (a-b)^(b-a)

集合工厂函数：

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
        """
        相当于s1-s2

        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

    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
        """
        与remove功能相同，删除元素不存在时不会抛出异常

        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
        """
        相当于s1&s2

        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
        """
        相当于s1<=s2

        Report whether another set contains this set. """
        pass

    def issuperset(self, *args, **kwargs): # real signature unknown
        """
        相当于s1>=s2

         Report whether this set contains another set. """
        pass

    def pop(self, *args, **kwargs): # real signature unknown
        """
        Remove and return an arbitrary set element.
        Raises KeyError if the set is empty.
        """
        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.
        """
        pass

    def symmetric_difference(self, *args, **kwargs): # real signature unknown
        """
        相当于s1^s2

        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
        """ Update a set with the symmetric difference of itself and another. """
        pass

    def union(self, *args, **kwargs): # real signature unknown
        """
        相当于s1|s2

        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

    def __and__(self, *args, **kwargs): # real signature unknown
        """ Return self&value. """
        pass

    def __contains__(self, y): # real signature unknown; restored from __doc__
        """ x.__contains__(y) <==> y in x. """
        pass

    def __eq__(self, *args, **kwargs): # real signature unknown
        """ Return self==value. """
        pass

    def __getattribute__(self, *args, **kwargs): # real signature unknown
        """ Return getattr(self, name). """
        pass

    def __ge__(self, *args, **kwargs): # real signature unknown
        """ Return self>=value. """
        pass

    def __gt__(self, *args, **kwargs): # real signature unknown
        """ Return self>value. """
        pass

    def __iand__(self, *args, **kwargs): # real signature unknown
        """ Return self&=value. """
        pass

    def __init__(self, seq=()): # known special case of set.__init__
        """
        set() -> new empty set object
        set(iterable) -> new set object

        Build an unordered collection of unique elements.
        # (copied from class doc)
        """
        pass

    def __ior__(self, *args, **kwargs): # real signature unknown
        """ Return self|=value. """
        pass

    def __isub__(self, *args, **kwargs): # real signature unknown
        """ Return self-=value. """
        pass

    def __iter__(self, *args, **kwargs): # real signature unknown
        """ Implement iter(self). """
        pass

    def __ixor__(self, *args, **kwargs): # real signature unknown
        """ Return self^=value. """
        pass

    def __len__(self, *args, **kwargs): # real signature unknown
        """ Return len(self). """
        pass

    def __le__(self, *args, **kwargs): # real signature unknown
        """ Return self<=value. """
        pass

    def __lt__(self, *args, **kwargs): # real signature unknown
        """ Return self<value. """
        pass

    @staticmethod # known case of __new__
    def __new__(*args, **kwargs): # real signature unknown
        """ Create and return a new object.  See help(type) for accurate signature. """
        pass

    def __ne__(self, *args, **kwargs): # real signature unknown
        """ Return self!=value. """
        pass

    def __or__(self, *args, **kwargs): # real signature unknown
        """ Return self|value. """
        pass

    def __rand__(self, *args, **kwargs): # real signature unknown
        """ Return value&self. """
        pass

    def __reduce__(self, *args, **kwargs): # real signature unknown
        """ Return state information for pickling. """
        pass

    def __repr__(self, *args, **kwargs): # real signature unknown
        """ Return repr(self). """
        pass

    def __ror__(self, *args, **kwargs): # real signature unknown
        """ Return value|self. """
        pass

    def __rsub__(self, *args, **kwargs): # real signature unknown
        """ Return value-self. """
        pass

    def __rxor__(self, *args, **kwargs): # real signature unknown
        """ Return value^self. """
        pass

    def __sizeof__(self): # real signature unknown; restored from __doc__
        """ S.__sizeof__() -> size of S in memory, in bytes """
        pass

    def __sub__(self, *args, **kwargs): # real signature unknown
        """ Return self-value. """
        pass

    def __xor__(self, *args, **kwargs): # real signature unknown
        """ Return self^value. """
        pass

    __hash__ = None

查看

查看

set工厂函数

练习：

 # 数据库中原有
 old_dict = {
     "#1":{ 'hostname':c1, 'cpu_count': 2, 'mem_capicity': 80 },
     "#2":{ 'hostname':c1, 'cpu_count': 2, 'mem_capicity': 80 }
     "#3":{ 'hostname':c1, 'cpu_count': 2, 'mem_capicity': 80 }
 }

 # cmdb 新汇报的数据
 new_dict = {
     "#1":{ 'hostname':c1, 'cpu_count': 2, 'mem_capicity': 800 },
     "#3":{ 'hostname':c1, 'cpu_count': 2, 'mem_capicity': 80 }
     "#4":{ 'hostname':c2, 'cpu_count': 2, 'mem_capicity': 80 }
 }

 #添加：旧数据不存在而新数据有的  new_set-olb_set
 #删除：新数据中没有，旧数据中存在的 old_set-new_set
 #更新：旧数据存在，新数据也存在而且内容变更  olb_set&new_set(且value不同)