1、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'])
2、查看set
>>> s1 {'gm', 'evescn', 'root'}
3、查看set可进行的操作
>>> dir(s1) ['__and__', '__class__', '__contains__', '__delattr__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__gt__', '__hash__', '__iand__', '__init__', '__ior__', '__isub__', '__iter__', '__ixor__', '__le__', '__len__', '__lt__', '__ne__', '__new__', '__or__', '__rand__', '__reduce__', '__reduce_ex__', '__repr__', '__ror__', '__rsub__', '__rxor__', '__setattr__', '__sizeof__', '__str__', '__sub__', '__subclasshook__', '__xor__', 'add', 'clear', 'copy', 'difference', 'difference_update', 'discard', 'intersection', 'intersection_update', 'isdisjoint', 'issubset', 'issuperset', 'pop', 'remove', 'symmetric_difference', 'symmetric_difference_update', 'union', 'update']
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 """ 添加 """ """ 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 """ 删除当前set中的所有包含在 new set 里的元素 """ """ Remove all elements of another set from this set. """ pass def discard(self, *args, **kwargs): # real signature unknown """ 移除元素 """ """ 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 """ 取交集，新创建一个set """ """ Return the intersection of two or more sets as a new set. (i.e. elements that are common to all of the sets.) """ pass def intersection_update(self, *args, **kwargs): # real signature unknown """ 取交集，修改原来set """ """ Update a set with the intersection of itself and another. """ pass def isdisjoint(self, *args, **kwargs): # real signature unknown """ 如果没有交集，返回true """ """ Return True if two sets have a null intersection. """ pass def issubset(self, *args, **kwargs): # real signature unknown """ 是否是子集 """ """ Report whether another set contains this set. """ pass def issuperset(self, *args, **kwargs): # real signature unknown """ 是否是父集 """ """ Report whether this set contains another set. """ pass def pop(self, *args, **kwargs): # real signature unknown """ 移除 """ """ Remove and return an arbitrary set element. Raises KeyError if the set is empty. """ pass def remove(self, *args, **kwargs): # real signature unknown """ 移除 """ """ 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 """ 差集，创建新对象""" """ 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 """ 差集，改变原来 """ """ Update a set with the symmetric difference of itself and another. """ pass def union(self, *args, **kwargs): # real signature unknown """ 并集 """ """ 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 """ 更新 """ """ Update a set with the union of itself and others. """ pass def __and__(self, y): # real signature unknown; restored from __doc__ """ x.__and__(y) <==> x&y """ pass def __cmp__(self, y): # real signature unknown; restored from __doc__ """ x.__cmp__(y) <==> cmp(x,y) """ pass def __contains__(self, y): # real signature unknown; restored from __doc__ """ x.__contains__(y) <==> y in x. """ pass def __eq__(self, y): # real signature unknown; restored from __doc__ """ x.__eq__(y) <==> x==y """ pass def __getattribute__(self, name): # real signature unknown; restored from __doc__ """ x.__getattribute__('name') <==> x.name """ pass def __ge__(self, y): # real signature unknown; restored from __doc__ """ x.__ge__(y) <==> x>=y """ pass def __gt__(self, y): # real signature unknown; restored from __doc__ """ x.__gt__(y) <==> x>y """ pass def __iand__(self, y): # real signature unknown; restored from __doc__ """ x.__iand__(y) <==> x&=y """ 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, y): # real signature unknown; restored from __doc__ """ x.__ior__(y) <==> x|=y """ pass def __isub__(self, y): # real signature unknown; restored from __doc__ """ x.__isub__(y) <==> x-=y """ pass def __iter__(self): # real signature unknown; restored from __doc__ """ x.__iter__() <==> iter(x) """ pass def __ixor__(self, y): # real signature unknown; restored from __doc__ """ x.__ixor__(y) <==> x^=y """ pass def __len__(self): # real signature unknown; restored from __doc__ """ x.__len__() <==> len(x) """ pass def __le__(self, y): # real signature unknown; restored from __doc__ """ x.__le__(y) <==> x<=y """ pass def __lt__(self, y): # real signature unknown; restored from __doc__ """ x.__lt__(y) <==> x<y """ pass @staticmethod # known case of __new__ def __new__(S, *more): # real signature unknown; restored from __doc__ """ T.__new__(S, ...) -> a new object with type S, a subtype of T """ pass def __ne__(self, y): # real signature unknown; restored from __doc__ """ x.__ne__(y) <==> x!=y """ pass def __or__(self, y): # real signature unknown; restored from __doc__ """ x.__or__(y) <==> x|y """ pass def __rand__(self, y): # real signature unknown; restored from __doc__ """ x.__rand__(y) <==> y&x """ pass def __reduce__(self, *args, **kwargs): # real signature unknown """ Return state information for pickling. """ pass def __repr__(self): # real signature unknown; restored from __doc__ """ x.__repr__() <==> repr(x) """ pass def __ror__(self, y): # real signature unknown; restored from __doc__ """ x.__ror__(y) <==> y|x """ pass def __rsub__(self, y): # real signature unknown; restored from __doc__ """ x.__rsub__(y) <==> y-x """ pass def __rxor__(self, y): # real signature unknown; restored from __doc__ """ x.__rxor__(y) <==> y^x """ pass def __sizeof__(self): # real signature unknown; restored from __doc__ """ S.__sizeof__() -> size of S in memory, in bytes """ pass def __sub__(self, y): # real signature unknown; restored from __doc__ """ x.__sub__(y) <==> x-y """ pass def __xor__(self, y): # real signature unknown; restored from __doc__ """ x.__xor__(y) <==> x^y """ pass __hash__ = None
4、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和remove的区别 # 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"
5、练习：寻找差异
1 # 数据库中原有 2 old_dict = { 3 "#1":{ 'hostname':c1, 'cpu_count': 2, 'mem_capicity': 80 }, 4 "#2":{ 'hostname':c1, 'cpu_count': 2, 'mem_capicity': 80 } 5 "#3":{ 'hostname':c1, 'cpu_count': 2, 'mem_capicity': 80 } 6 } 7 8 # cmdb 新汇报的数据 9 new_dict = { 10 "#1":{ 'hostname':c1, 'cpu_count': 2, 'mem_capicity': 800 }, 11 "#3":{ 'hostname':c1, 'cpu_count': 2, 'mem_capicity': 80 } 12 "#4":{ 'hostname':c2, 'cpu_count': 2, 'mem_capicity': 80 } 13 } 14 15 需要删除：？ 16 需要新建：？ 17 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
结果：
1 交集、差集即为需要的结果 2 3 交集： 4 需要更新或不变的数据 5 6 差集： 7 old差new --> 删除的数据 8 new差old --> 新增的数据 9 10 # 获取字典的key值 11 old = set(old_dict.keys()) 12 new = set(new_dict.keys()) 13 14 update_set = old.intersection(new) #要更新的集合 15 delete_set = old.difference(update_set) ) #要删除的集合 16 add_set = new.difference(update_set) #要添加的集合