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?
解决方案是:
DICT_RESERVED_KEYS = vars(dict).keys()
class SmartDict(dict):
"""
A Dict which is accessible via attribute dot notation
"""
def __init__(self, *args, **kwargs):
"""
:param args: multiple dicts ({}, {}, ..)
:param kwargs: arbitrary keys='value'
If ``keyerror=False`` is passed then not found attributes will
always return None.
"""
super(SmartDict, self).__init__()
self['__keyerror'] = kwargs.pop('keyerror', True)
[self.update(arg) for arg in args if isinstance(arg, dict)]
self.update(kwargs)
def __getattr__(self, attr):
if attr not in DICT_RESERVED_KEYS:
if self['__keyerror']:
return self[attr]
else:
return self.get(attr)
return getattr(self, attr)
def __setattr__(self, key, value):
if key in DICT_RESERVED_KEYS:
raise AttributeError("You cannot set a reserved name as attribute")
self.__setitem__(key, value)
def __copy__(self):
return self.__class__(self)
def copy(self):
return self.__copy__()
这并没有解决最初的问题,但是对于像我这样在这里寻找提供此功能的库的人来说应该是有用的。
Addict是一个很棒的库:https://github.com/mewwts/addict它照顾了前面的答案中提到的许多问题。
文档中的一个例子:
body = {
'query': {
'filtered': {
'query': {
'match': {'description': 'addictive'}
},
'filter': {
'term': {'created_by': 'Mats'}
}
}
}
}
成瘾者:
from addict import Dict
body = Dict()
body.query.filtered.query.match.description = 'addictive'
body.query.filtered.filter.term.created_by = 'Mats'
为了给答案增加一些变化,sci-kit learn将其实现为一串:
class Bunch(dict):
""" Scikit Learn's container object
Dictionary-like object that exposes its keys as attributes.
>>> b = Bunch(a=1, b=2)
>>> b['b']
2
>>> b.b
2
>>> b.c = 6
>>> b['c']
6
"""
def __init__(self, **kwargs):
super(Bunch, self).__init__(kwargs)
def __setattr__(self, key, value):
self[key] = value
def __dir__(self):
return self.keys()
def __getattr__(self, key):
try:
return self[key]
except KeyError:
raise AttributeError(key)
def __setstate__(self, state):
pass
您所需要的是获取setattr和getattr方法—getattr检查字典键,然后继续检查实际属性。setstaet是针对pickle /unpickling“bunch”的修复-如果感兴趣,请检查https://github.com/scikit-learn/scikit-learn/issues/6196