如何将带有插槽的 python 类转换为字典? [英] How can I convert python class with slots to dictionary?

问题描述

我正在使用带插槽的类来减少实例将占用的内存.现在，如何将插槽实例转换为字典?

槽类看起来像这样:

class Foo(object):__slots__ = ['x','y','z']def __init__(self):自我.x = 1自我.y = 2self.z = 3

我期待这样的事情:

y = Foo()y.__dict__{'x':1，'y':2，'z':3}

解决方案

使用 __slots__ 属性加上 getattr() 在字典理解中:

{s: getattr(obj, s) for s in obj.__slots__ if hasattr(obj, s)}

跳过任何未设置的属性.

替代方法，将缺少的属性设置为 None:

{s: getattr(obj, s, None) for s in obj.__slots__}

演示:

<预><代码>>>>类 Foo(对象):... __slots__ = ('bar', '垃圾邮件')...>>>obj = Foo()>>>obj.bar = 42>>>{s: getattr(obj, s) for s in obj.__slots__ if hasattr(obj, s)}{'条':42}>>>{s: getattr(obj, s, None) for s in obj.__slots__}{'垃圾邮件':无，'bar':42}

您甚至可以将其设为类的属性，vars() 将使用它:

<预><代码>>>>类 Foo(对象):... __slots__ = ('bar', '垃圾邮件')... @财产... def __dict__(self):... return {s: getattr(self, s) for s in self.__slots__ if hasattr(self, s)}...>>>f = Foo()>>>f.bar = 42>>>f.__dict__{'条':42}>>>f.spam = '鸡蛋'>>>f.__dict__{'垃圾邮件':'鸡蛋'，'酒吧':42}>>>变量(f){'垃圾邮件':'鸡蛋'，'酒吧':42}>>>f.hello = '世界'回溯(最近一次调用最后一次):文件<stdin>"，第 1 行，位于 <module>AttributeError: 'Foo' 对象没有属性 'hello'

I am using class with slots to reduce the memory which the instance will occupy. Now, how can I convert a slot instance to dictionary ?

The slot class look like this :

class Foo(object):
       __slots__ = ['x','y','z']
       def __init__(self):
           self.x = 1
           self.y = 2 
           self.z = 3

I expect something like this:

y = Foo()
y.__dict__
{'x': 1, 'y': 2, 'z': 3}

解决方案

Use the __slots__ attribute plus getattr() in a dictionary comprehension:

{s: getattr(obj, s) for s in obj.__slots__ if hasattr(obj, s)}

which skips any attributes not set.

Alternative, setting missing attributes to None:

{s: getattr(obj, s, None) for s in obj.__slots__}

Demo:

>>> class Foo(object):
...     __slots__ = ('bar', 'spam')
... 
>>> obj = Foo()
>>> obj.bar = 42
>>> {s: getattr(obj, s) for s in obj.__slots__ if hasattr(obj, s)}
{'bar': 42}
>>> {s: getattr(obj, s, None) for s in obj.__slots__}
{'spam': None, 'bar': 42}

You can even make that a property of the class and vars() will make use of it:

>>> class Foo(object):
...     __slots__ = ('bar', 'spam')
...     @property
...     def __dict__(self):
...         return {s: getattr(self, s) for s in self.__slots__ if hasattr(self, s)}
... 
>>> f = Foo()
>>> f.bar = 42
>>> f.__dict__
{'bar': 42}
>>> f.spam = 'eggs'
>>> f.__dict__
{'spam': 'eggs', 'bar': 42}
>>> vars(f)
{'spam': 'eggs', 'bar': 42}
>>> f.hello = 'world'
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'Foo' object has no attribute 'hello'

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