有什么技巧可以“重载点运算符"吗? [英] Is there any trick to "overload the dot operator"?

问题描述

我知道这个问题有点奇怪，但是我想不出其他任何方式来表达.我有一个处理大型json对象的应用程序，我希望能够说:

I know the question is a little weirdly stated, but I can't think of any other way of saying it. I have an application that deals with large json objects, and I want to be able to just say:

object1.value.size.whatever.attributexyz

代替

object1.get('value').get('size').get('whatever').get('attributexyz')

是否有一些聪明的方法来捕获将要引发的AttributeError并检查数据结构内部的属性是否对应于其任何值?

Is there some clever way to catch the AttributeError that would be raised and check inside the data structure if that attribute corresponds to any of its values?

推荐答案

在object1的类定义中，

def __getattr__(self, key):
    return self.get(key)

任何尝试解析对象本身上实际上不存在的属性，方法或字段名称的尝试都将传递给

Any attempt to resolve a property, method, or field name that doesn't actually exist on the object itself will be passed to __getattr__.

如果您无权访问类定义，即类似于字典，则将其包装在类中.对于字典，您可以执行以下操作:

If you don't have access to the class definition, i.e. it's something like a dictionary, wrap it in a class. For a dictionary, you could do something like:

class DictWrapper(object):
    def __init__(self, d):
        self.d = d
    def __getattr__(self, key):
        return self.d[key]

请注意，如果密钥无效，则会引发KeyError；否则，将引发KeyError.但是，约定是引发AttributeError(感谢S. Lott！).您可以像这样重新引发KeyError作为AttributeError:

Note that a KeyError will be raised if the key is invalid; the convention, however, is to raise an AttributeError (thanks, S. Lott!). You can re-raise the KeyError as an AttributeError like so, if necessary:

try:
    return self.get(key)
except KeyError as e:
    raise AttributeError(e)

还请记住，如果您从__getattr__返回的对象也是字典，那么您也需要将它们包装起来.

Also remember that if the objects you are returning from __getattr__ are also, for example, dictionaries, you'll need to wrap them too.

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