嵌套子对象/链接属性上的 getattr 和 setattr？

Question

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：

 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__

目前我得到错误的输出： {'pet': <__main__.Pet object at 0x10c5ec050>, 'residence': <__main__.Residence object at 0x10c5ec0d0>, 'pet.name': 'Sparky', 'residence.type': 'Apartment'}

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 Person 。

• 我无法将 person.pet 指定为 setattr() 因为不同的子对象将通过相同的方法设置，如果/当找到相关键时解析一些文本并填充对象属性。

• 有没有简单/内置的方法来完成这个？

• 或者我可能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() 在找到的子对象上？

原文由 TPB 发布，翻译遵循 CC BY-SA 4.0 许可协议

Answer 1

您可以使用 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 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

原文由 unutbu 发布，翻译遵循 CC BY-SA 3.0 许可协议

Answer 2

对于开箱即用的解决方案，您可以使用 operator.attrgetter ：

 from operator import attrgetter
attrgetter(dotted_path)(obj)

原文由 Milo Wielondek 发布，翻译遵循 CC BY-SA 4.0 许可协议