问题描述
我有一个对象 (Person),它有多个子对象 (Pet, Residence) 作为属性.我希望能够像这样动态设置这些子对象的属性:
I have an object (Person) that has multiple subobjects (Pet, Residence) as properties. I want to be able to dynamically set the properties of these subobjects like so:
class Person(object): def __init__(self): self.pet = Pet() self.residence = Residence() class Pet(object): def __init__(self,name='Fido',species='Dog'): self.name = name self.species = species class Residence(object): def __init__(self,type='House',sqft=None): self.type = type self.sqft=sqft if __name__=='__main__': p=Person() setattr(p,'pet.name','Sparky') setattr(p,'residence.type','Apartment') print p.__dict__
目前我得到了错误的输出:{'pet': <__main__.Pet object at 0x10c5ec050>, 'residence': <__main__.Residence object at 0x10c5ec0d0>, 'pet.name': 'Sparky', 'residence.type': '公寓'}
Currently I get the wrong output: {'pet': <__main__.Pet object at 0x10c5ec050>, 'residence': <__main__.Residence object at 0x10c5ec0d0>, 'pet.name': 'Sparky', 'residence.type': 'Apartment'}
如您所见,不是在 Person 的 Pet 子对象上设置 name 属性,而是一个新属性 pet.name 是在 Person 上创建的.
As you can see, instead of setting the name attribute on the Pet subobject of the Person, a new attribute pet.name is created on the Person.
我无法将person.pet指定为setattr(),因为不同的子对象会被同一个方法设置,解析一些文本并填写如果/当找到相关键时,对象属性.
I cannot specify person.pet to setattr() because different sub-objects will be set by the same method, which parses some text and fills in the object attributes if/when a relevant key is found.
有没有一种简单/内置的方法来完成这个?
Is there a easy/builtin way to accomplish this?
或者也许我需要编写一个递归函数来解析字符串并多次调用 getattr() 直到找到必要的子对象然后调用 setattr()找到的子对象上的代码>?
Or perhaps I need to write a recursive function to parse the string and call getattr() multiple times until the necessary subobject is found and then call setattr() on that found subobject?
推荐答案
你可以使用 functools.reduce:
You could use functools.reduce:
import functools def rsetattr(obj, attr, val): pre, _, post = attr.rpartition('.') return setattr(rgetattr(obj, pre) if pre else obj, post, val) # using wonder's beautiful simplification: https://stackoverflow.com/questions/31174295/getattr-and-setattr-on-nested-objects/31174427?noredirect=1#comment86638618_31174427 def rgetattr(obj, attr, *args): def _getattr(obj, attr): return getattr(obj, attr, *args) return functools.reduce(_getattr, [obj] + attr.split('.'))
rgetattr 和 rsetattr 是 getattr 和 setattr 的直接替换,它还可以处理带点的 attr 字符串.
rgetattr and rsetattr are drop-in replacements for getattr and setattr, which can also handle dotted attr strings.
import functools class Person(object): def __init__(self): self.pet = Pet() self.residence = Residence() class Pet(object): def __init__(self,name='Fido',species='Dog'): self.name = name self.species = species class Residence(object): def __init__(self,type='House',sqft=None): self.type = type self.sqft=sqft def rsetattr(obj, attr, val): pre, _, post = attr.rpartition('.') return setattr(rgetattr(obj, pre) if pre else obj, post, val) def rgetattr(obj, attr, *args): def _getattr(obj, attr): return getattr(obj, attr, *args) return functools.reduce(_getattr, [obj] + attr.split('.'))
<小时>
if __name__=='__main__': p = Person() print(rgetattr(p, 'pet.favorite.color', 'calico')) # 'calico' try: # Without a default argument, `rgetattr`, like `getattr`, raises # AttributeError when the dotted attribute is missing print(rgetattr(p, 'pet.favorite.color')) except AttributeError as err: print(err) # 'Pet' object has no attribute 'favorite' rsetattr(p, 'pet.name', 'Sparky') rsetattr(p, 'residence.type', 'Apartment') print(p.__dict__) print(p.pet.name) # Sparky print(p.residence.type) # Apartment