设置和获取束类型对象的属性

Question

为了简化解析/创建JSON，机器学习应用程序通常使用Bunch对象，例如https://github.com/dsc/bunch/blob/master/bunch/__init__.py

获取时，有一个嵌套的EAFP习惯用法，它检查dict.get()函数，然后尝试使用字典方括号语法访问它，即

class Bunch(dict):
def __getattr___(self, k):
try:
return object.__getattribute__(self, k)
except AttributeError:
try: 
return self[k]
except KeyError:
raise AttributeError

当尝试设置属性时，

def __setattr__(self, k, v):
try:
# Throws exception if not in prototype chain
object.__getattribute__(self, k)
except AttributeError:
try:
self[k] = v
except:
raise AttributeError(k)
else:
object.__setattr__(self, k, v)

似乎sklearn的实现遵循相同的思路，但检查较少https://github.com/scikit-learn/scikit-learn/blob/2beed5584/sklearn/utils/__init__.py#L61

class Bunch(dict):
def __init__(self, **kwargs):
super().__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):
# Bunch pickles generated with scikit-learn 0.16.* have an non
# empty __dict__. This causes a surprising behaviour when
# loading these pickles scikit-learn 0.17: reading bunch.key
# uses __dict__ but assigning to bunch.key use __setattr__ and
# only changes bunch['key']. More details can be found at:
# https://github.com/scikit-learn/scikit-learn/issues/6196.
# Overriding __setstate__ to be a noop has the effect of
# ignoring the pickled __dict__
pass

嵌套的EAFP似乎有点难以维护，我的问题是:

• 是否有一种更简单的方法来处理get和set函数的束数据对象?
• 是否有其他类似Dict的对象允许属性和键之间的可变性?
• 束对象的.update()函数应该如何工作，浅复制还是深复制?还是让默认的dict.update()做它该做的?理解dict.copy() -浅还是深?

Answer 1

幸运的是，所有对象都有一个内部的类似字典的对象来管理对象的属性(这是在__dict__属性中)。要做您所要求的，您只需要使类使用自己作为__dict__对象:

class Bunch(dict):
def __init__(self, *args, **kwargs):
self.__dict__ = self
super().__init__(*args, **kwargs)

用法:

>>> b = Bunch()
>>> b.foo = 3
>>> b["foo"]
3
>>> b["foo"] = 5
>>> b.foo
5
>>> b["bar"] = 1
>>> b.bar
1