OrderedDict不会在类中排序 [英] OrderedDict won't sort within a class
问题描述
我有一个父类,我想要保持其子类的所有实例的注册表(以字典的形式)。很容易,但我想注册表根据自己的键排序,这是初始化的2个子类的参数。这是我的代码以简化的形式:
I have a parent class, and I want to keep a registry (in the form of a dictionary) of all instances of its sub-classes. Easy, but I want the registry to sort itself based on its keys, which are the arguments of the 2 sub-classes on initialisation. This is my code in simplified form:
from collections import OrderedDict
class Parent:
_registry = OrderedDict()
def __init__(self):
# add each sub-class instance to the registry & sort the registry
self._registry.update({self._num:self})
self._registry = OrderedDict(sorted(self._registry.items()))
class Foo(Parent):
def __init__(self, number):
self._num = number
Parent.__init__(self)
# then do some stuff
class Bar(Parent):
def __init__(self, number):
self._num = number
Parent.__init__(self)
# then do some other stuff
...
但是,尽管注册表使用新的子类对象,它不会自己排序。
But, although the registry updates itself with the new sub-class objects, it does not sort itself.
>>> a = Foo(3)
>>> Parent._registry # check to see if a was added to the registry
OrderedDict([(3, <Foo instance at 0x00A19C0C8>)])
>>> b = Bar(1)
>>> Parent._registry # check to see if b was inserted before a in the registry
OrderedDict([(3, <Foo instance at 0x00A19C0C8>), (1, <Bar instance at 0x00A19C1C8>)])
b
comes after a
in the registry!
如果我在iPython控制台中手动执行,它的工作原理:
If I do it manually in the iPython console, it works:
>>> Parent._registry = OrderedDict(sorted(Parent._registry.items()))
OrderedDict([(1, <Bar instance at 0x00A19C1C8>), (3, <Foo instance at 0x00A19C0C8>)])
为什么不排序?我需要它,因为以后,事情必须发生在这些对象严格的顺序他们数字
参数。
Why won't it sort itself? I need it to, because later on, things have to happen to those objects in strict order of their number
arguments.
推荐答案
这是因为:
self._registry = OrderedDict(sorted(self._registry.items()))
在实例上创建一个新的attrbute, c $ c> Parent._registry 。
creates a new attrbute on the instance, this doesn't affect Parent._registry
.
将此行替换为:
Parent._registry = OrderedDict(sorted(self._registry.items()))
这里 self._registry.items()
可以获取 Parent._registry
的值, self._registry
的作业将影响 Parent._registry
。
Here self._registry.items()
can fetch the value of Parent._registry
but that doesn't mean assignment to self._registry
will affect Parent._registry
.
使用 self._registry
本身的另一种方法:
Another way to do it using self._registry
itself:
def __init__(self):
items = sorted(self._registry.items() + [(self._num, self)]) #collect items
self._registry.clear() #clean the dict
self._registry.update(items) #now update it
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