我发现它更方便访问字典键作为obj。foo而不是obj['foo'],所以我写了这个片段:
class AttributeDict(dict):
def __getattr__(self, attr):
return self[attr]
def __setattr__(self, attr, value):
self[attr] = value
然而,我认为一定有一些原因,Python没有提供开箱即用的功能。以这种方式访问字典键的注意事项和缺陷是什么?
由于以下原因,我对现有的选项不满意,于是我开发了MetaDict。它的行为完全类似于dict,但支持点表示法和IDE自动补全,而没有其他解决方案的缺点和潜在的名称空间冲突。所有功能和使用示例都可以在GitHub上找到(见上面的链接)。
完全披露:我是MetaDict的作者。
我在尝试其他解决方案时遇到的缺点/限制:
Addict
No key autocompletion in IDE
Nested key assignment cannot be turned off
Newly assigned dict objects are not converted to support attribute-style key access
Shadows inbuilt type Dict
Prodict
No key autocompletion in IDE without defining a static schema (similar to dataclass)
No recursive conversion of dict objects when embedded in list or other inbuilt iterables
AttrDict
No key autocompletion in IDE
Converts list objects to tuple behind the scenes
Munch
Inbuilt methods like items(), update(), etc. can be overwritten with obj.items = [1, 2, 3]
No recursive conversion of dict objects when embedded in list or other inbuilt iterables
EasyDict
Only strings are valid keys, but dict accepts all hashable objects as keys
Inbuilt methods like items(), update(), etc. can be overwritten with obj.items = [1, 2, 3]
Inbuilt methods don't behave as expected: obj.pop('unknown_key', None) raises an AttributeError
这个答案摘自Luciano Ramalho的《流利的Python》一书。这要归功于那个家伙。
class AttrDict:
"""A read-only façade for navigating a JSON-like object
using attribute notation
"""
def __init__(self, mapping):
self._data = dict(mapping)
def __getattr__(self, name):
if hasattr(self._data, name):
return getattr(self._data, name)
else:
return AttrDict.build(self._data[name])
@classmethod
def build(cls, obj):
if isinstance(obj, Mapping):
return cls(obj)
elif isinstance(obj, MutableSequence):
return [cls.build(item) for item in obj]
else:
return obj
in the init we are taking the dict and making it a dictionary. when getattr is used we try to get the attribute from the dict if the dict already has that attribute. or else we are passing the argument to a class method called build. now build does the intresting thing. if the object is dict or a mapping like that, the that object is made an attr dict itself. if it's a sequence like list, it's passed to the build function we r on right now. if it's anythin else, like str or int. return the object itself.
让我发布另一个实现,它基于Kinvais的答案,但集成了http://databio.org/posts/python_AttributeDict.html中提出的AttributeDict的思想。
这个版本的优点是它也适用于嵌套字典:
class AttrDict(dict):
"""
A class to convert a nested Dictionary into an object with key-values
that are accessible using attribute notation (AttrDict.attribute) instead of
key notation (Dict["key"]). This class recursively sets Dicts to objects,
allowing you to recurse down nested dicts (like: AttrDict.attr.attr)
"""
# Inspired by:
# http://stackoverflow.com/a/14620633/1551810
# http://databio.org/posts/python_AttributeDict.html
def __init__(self, iterable, **kwargs):
super(AttrDict, self).__init__(iterable, **kwargs)
for key, value in iterable.items():
if isinstance(value, dict):
self.__dict__[key] = AttrDict(value)
else:
self.__dict__[key] = value
这不是一个“好”的答案,但我认为这是俏皮的(它不处理嵌套字典在当前形式)。简单地将dict包装在函数中:
def make_funcdict(d=None, **kwargs)
def funcdict(d=None, **kwargs):
if d is not None:
funcdict.__dict__.update(d)
funcdict.__dict__.update(kwargs)
return funcdict.__dict__
funcdict(d, **kwargs)
return funcdict
现在你的语法略有不同。访问dict项就像访问属性f.key一样。要以通常的方式访问dict项(和其他dict方法),请执行f()['key'],我们可以通过使用关键字参数和/或字典调用f来方便地更新dict
例子
d = {'name':'Henry', 'age':31}
d = make_funcdict(d)
>>> for key in d():
... print key
...
age
name
>>> print d.name
... Henry
>>> print d.age
... 31
>>> d({'Height':'5-11'}, Job='Carpenter')
... {'age': 31, 'name': 'Henry', 'Job': 'Carpenter', 'Height': '5-11'}
就是这样。如果有人提出这种方法的优点和缺点,我会很高兴。
你可以从标准库中获取一个方便的容器类:
from argparse import Namespace
避免复制代码位。没有标准的字典访问,但如果你真的想要的话,很容易得到一个。argparse中的代码很简单,
class Namespace(_AttributeHolder):
"""Simple object for storing attributes.
Implements equality by attribute names and values, and provides a simple
string representation.
"""
def __init__(self, **kwargs):
for name in kwargs:
setattr(self, name, kwargs[name])
__hash__ = None
def __eq__(self, other):
return vars(self) == vars(other)
def __ne__(self, other):
return not (self == other)
def __contains__(self, key):
return key in self.__dict__
很抱歉再添加一个,但这一个解决了subdicts和纠正AttributeError,尽管非常简单:
class DotDict(dict):
def __init__(self, d: dict = {}):
super().__init__()
for key, value in d.items():
self[key] = DotDict(value) if type(value) is dict else value
def __getattr__(self, key):
if key in self:
return self[key]
raise AttributeError(key) #Set proper exception, not KeyError
__setattr__ = dict.__setitem__
__delattr__ = dict.__delitem__