为什么自定义类型接受 Python 中的临时属性（而内置类型不接受）？
我想知道为什么人们能够为自定义类型的实例创建一个新属性（“新”意味着“先前未在类主体中定义”），但无法为内置类型执行相同的操作在类型上，就像object本身一样。
代码示例：
>>> class SomeClass(object):
... pass
...
>>> sc = SomeClass()
>>> sc.name = "AAA"
>>> sc.name
'AAA'
>>> obj = object()
>>> obj.name = "BBB"
Traceback (most recent call last):
File "<console>", line 1, in <module>
AttributeError: 'object' object has no attribute 'name'
I'd like to know why one is able to create a new attribute ("new" means "not previously defined in the class body") for an instance of a custom type, but is not able to do the same for a built-in type, like object itself.
A code example:
>>> class SomeClass(object):
... pass
...
>>> sc = SomeClass()
>>> sc.name = "AAA"
>>> sc.name
'AAA'
>>> obj = object()
>>> obj.name = "BBB"
Traceback (most recent call last):
File "<console>", line 1, in <module>
AttributeError: 'object' object has no attribute 'name'
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有些对象没有 __dict__ 属性（这是存储所有自定义“新定义”属性的字典）。您可以使用 __slots__ 变量模拟相同的行为（请参阅 Python 参考）。当您使用 __dict__ 子类化类时，__slots__ 变量不起作用。由于您始终为新样式类创建 object 子类，因此 object 不得具有 __dict__，因为这将导致无法使用 __slots__。没有 __slots__ 的类占用更少的内存，并且速度可能稍快一些。
Some objects don't have the __dict__ attribute (which is a dictionary that stores all the custom 'newly defined' attributes). You can emulate the same behaviour using the __slots__ variable (see python reference). When you are subclassing a class with __dict__, the __slots__ variable has no effect. And as you are always subclassing object for new style classes, the object mustn't have __dict__, as that would make it impossible to use __slots__. The classes without __slots__ take less memory and are probably slightly faster.