Set 数据类型
一、创建一个 set
# set和dict类似，也是一组key的集合，但不存储value。由于key不能重复，所以，在set中，没有重复的key。
# 访问速度快，天生解决了重复问题
>>> s1 = set(['root', 'gm', 'evescn', 'gm'])
二、查看 set
>>> s1
{'gm', 'evescn', 'root'}
三、查看 set 可进行的操作
>>> dir(s1)
['add', 'clear', 'copy', 'difference', 'difference_update', 'discard', 'intersection', 'intersection_update', 'isdisjoint', 'issubset', 'issuperset', 'pop', 'remove', 'symmetric_difference', 'symmetric_difference_update', 'union', 'update']
set 函数方法
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
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
"""
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
"""
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
"""
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
"""
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 __class_getitem__(self, *args, **kwargs): # real signature unknown
""" See PEP 585 """
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
四、常用的 set 操作
# 添加一个新的key
>>> s1
{'gm', 'evescn', 'root'}
>>> s1.add('gm')
>>> s1
{'gm', 'evescn', 'root'}
# s1和s2对比
>>> s1
{'gm', 'evescn', 'root'}
>>> s2
{'gm', 'root', 'hlr'}
>>> s1.difference(s2) # s1差s2
{'evescn'}
>>> s2.difference(s1) # s2差s1
{'hlr'}
>>> s1.intersection(s2) # s1交s2
{'gm', 'root'}
>>> s1.union(s2) # s1并s2
{'gm', 'root', 'hlr', 'evescn'}
- difference和difference_update的区别
# difference把差异结果返回，但不修改原集合
# difference_update修改原集合# 其他操作，例如：intersection和intersection_update也是类似的
>>> s1
{'gm', 'evescn', 'root'}
>>> s2
{'gm', 'root', 'hlr'}
>>> s2.difference(s1)
{'hlr'}
>>> s3 = s2.difference(s1)
>>> s3 # s3获取到了difference返回的结果
{'hlr'}
>>> s2 # s2未被修改
{'gm', 'root', 'hlr'}
>>> s4 = s2.difference_update(s1)
>>> s4 # difference_updat没有返回结果
>>> s2 # s2已经被修改
{'hlr'}
# pop：删除一个key值，并且删除的key可以使用变量来获取，不支持删除指定的key值
# remove：删除指定的key值，不能获取到删除的key值，不指定key值会报错
>>> s1
{'gm', 'evescn', 'root', 'abc'}
>>> set1 = s1.pop('gm') # 指定key值报错
Traceback (most recent call last):
File "<pyshell#158>", line 1, in <module>
set1 = s1.pop('gm')
TypeError: pop() takes no arguments (1 given)
>>> set1 = s1.pop()
>>> set1 # 获取到删除的key
'gm'
>>> s1
{'evescn', 'root', 'abc'}
>>> set2 = s1.pop()
>>> set2
'evescn'
>>> s1
{'root', 'abc'}
>>> set3 = s1.remove() # 删除时，不指定key值报错
Traceback (most recent call last):
File "<pyshell#152>", line 1, in <module>
set3 = s1.remove()
TypeError: remove() takes exactly one argument (0 given)
>>> set3 = s1.remove('abc')
>>> set3 # 不能获取到删除的key
>>> s1
{'root'}
# 差集和对称差的区别
>>> s1
{'gm', 'evescn', 'root'}
>>> s2
{'gm', 'hlr', 'root'}
# 差集
>>> ret1 = s1.difference(s2)
>>> ret2 = s2.difference(s1)
>>> print(ret1)
{'evescn'}
>>> print(ret2)
{'hlr'}
# 简单的理解如何计算出差集的
for item in s1:
if item in s2:
del "s1.item"
# 对称差
ret1 = s1.symmetric_difference(s2)
ret2 = s2.symmetric_difference(s1)
>>> print(ret1)
{'evescn', 'hlr'}
>>> print(ret2)
{'evescn', 'hlr'}
# 如何计算出对称差的
for item in s1:
if item not in s2:
add "ret1.item"
for item in s2:
if item not in s1:
add "ret1.item"
五、练习：寻找差异
# 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 }
}
需要删除：？
需要新建：？
需要更新：？ 注意：无需考虑内部元素是否改变，只要原来存在，新汇报也存在，就是需要更新
交集、差集即为需要的结果
交集：
需要更新或不变的数据
差集：
old差new --> 删除的数据
new差old --> 新增的数据
# 获取字典的key值
old = set(old_dict.keys())
new = set(new_dict.keys())
update_set = old.intersection(new) #要更新的集合
delete_set = old.difference(update_set) ) #要删除的集合
add_set = new.difference(update_set) #要添加的集合
