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.pettosetattr()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()?
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
这篇关于嵌套子对象/链式属性上的 getattr 和 setattr?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持跟版网！