嵌套子对象/链接属性上的getattr和setattr? [英] getattr and setattr on nested subobjects / chained properties?

问题描述

我有一个对象(Person)，该对象具有多个子对象(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__

当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': 'Apartment'}

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，而是在Person上创建了一个新的属性pet.name.

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.

• 我无法指定person.pet至setattr()，因为将通过相同的方法设置不同的子对象，该方法将解析某些文本并在找到相关关键字时填充对象属性.

• 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.

是否有简单/内置的方式来完成此任务?

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，然后在找到的子对象上调用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

您可以使用

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的直接替代品， 也可以处理点缀的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('.'))

---

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/链接属性上的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IT屋！