通过属性和索引访问字典的递归方法？

Question

我想要能够做到类似这样的事情：

from dotDict import dotdictify

life = {'bigBang':
           {'stars':
               {'planets': []}
           }
       }

dotdictify(life)

# This would be the regular way:
life['bigBang']['stars']['planets'] = {'earth': {'singleCellLife': {}}}
# But how can we make this work?
life.bigBang.stars.planets.earth = {'singleCellLife': {}}

#Also creating new child objects if none exist, using the following syntax:
life.bigBang.stars.planets.earth.multiCellLife = {'reptiles':{},'mammals':{}}

我这么做的原因是想让代码更简洁，如果可以的话，想用和JavaScript类似的语法来访问JSON对象，这样可以更高效地进行跨平台开发。（我也使用Py2JS和类似的工具。）

Answer 1

有一个工具包正好能满足你的需求，而且还有更多功能，叫做 Prodict。

from prodict import Prodict

life_dict = {'bigBang':
                {'stars':
                    {'planets': []}
                }
            }

life = Prodict.from_dict(life_dict)

print(life.bigBang.stars.planets)
# prints []

# you can even add new properties dynamically
life.bigBang.galaxies = []

附言：我是 Prodict 的作者。

Answer 2

下面是一个嵌套属性字典的另一种实现方式（灵感来自Curt Hagenlocher的回答，简化到最基本的部分）：

class AttrDict(dict):
    """ Nested Attribute Dictionary

    A class to convert a nested Dictionary into an object with key-values
    accessible using attribute notation (AttrDict.attribute) in addition to
    key notation (Dict["key"]). This class recursively sets Dicts to objects,
    allowing you to recurse into nested dicts (like: AttrDict.attr.attr)
    """

    def __init__(self, mapping=None):
        super(AttrDict, self).__init__()
        if mapping is not None:
            for key, value in mapping.items():
                self.__setitem__(key, value)

    def __setitem__(self, key, value):
        if isinstance(value, dict):
            value = AttrDict(value)
        super(AttrDict, self).__setitem__(key, value)
        self.__dict__[key] = value  # for code completion in editors

    def __getattr__(self, item):
        try:
            return self.__getitem__(item)
        except KeyError:
            raise AttributeError(item)

    __setattr__ = __setitem__

这个实现可以在Python 2和Python 3中都能运行：

life = AttrDict({'bigBang': {'stars': {'planets': {}}}})
life['bigBang']['stars']['planets'] = {'earth': {'singleCellLife': {}}}
life.bigBang.stars.planets.earth.multiCellLife = {'reptiles': {}, 'mammals': {}}
print(life.bigBang.stars.planets.earth)
# -> {'singleCellLife': {}, 'multiCellLife': {'mammals': {}, 'reptiles': {}}}

在__getattr__中将KeyError转换为AttributeError是Python 3中的一个要求，这样即使找不到属性，hasattr也能正常工作：

hasattr(life, 'parallelUniverse')
# --> False

Answer 3

这里有一种方法可以实现那种体验：

class DotDictify(dict):
    MARKER = object()

    def __init__(self, value=None):
        if value is None:
            pass
        elif isinstance(value, dict):
            for key in value:
                self.__setitem__(key, value[key])
        else:
            raise TypeError('expected dict')

    def __setitem__(self, key, value):
        if isinstance(value, dict) and not isinstance(value, DotDictify):
            value = DotDictify(value)
        super(DotDictify, self).__setitem__(key, value)

    def __getitem__(self, key):
        found = self.get(key, DotDictify.MARKER)
        if found is DotDictify.MARKER:
            found = DotDictify()
            super(DotDictify, self).__setitem__(key, found)
        return found

    __setattr__, __getattr__ = __setitem__, __getitem__


if __name__ == '__main__':

    life = {'bigBang':
               {'stars':
                   {'planets': {}  # Value changed from []
                   }
               }
           }

    life = DotDictify(life)
    print(life.bigBang.stars.planets)  # -> []
    life.bigBang.stars.planets.earth = {'singleCellLife' : {}}
    print(life.bigBang.stars.planets)  # -> {'earth': {'singleCellLife': {}}}