为什么Python的空类和函数作为任意数据容器工作,而不是其他对象？

Question

我已经看到两个不同的Python对象用于将任意数据组合在一起:空类和函数.

def struct():
    pass

record = struct
record.number = 3
record.name = "Zoe"


class Struct:
    pass

record = Struct()
record.number = 3
record.name = "Zoe"

即使该类不为空,只要它在运行时定义,它似乎也可以工作.

但是当我自大并试图用内置函数或类来做这件事时,它没有用.

record = set()
record.number = 3
AttributeError: 'set' object has no attribute 'number'

record = pow
pow.number = 3
AttributeError: 'builtin_function_or_method' object has no attribute 'number'

内置和"自定义"类和函数之间是否存在根本区别？

Answer 1

区别在于函数对象和Struct对象都有一个__dict__属性,但set实例和内置函数不具有:

>>> def struct():
...     pass
...
>>> record = struct
>>> record.number = 2
>>> struct.__dict__
{'number': 2}
>>> class Struct:
...     pass
...
>>> record = Struct()
>>> record.number = 3
>>> record.__dict__
{'number': 3}
>>> record=set()
>>> record.__dict__
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'set' object has no attribute '__dict__'
>>> pow.__dict__
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'builtin_function_or_method' object has no attribute '__dict__'

您可以使用插槽来模拟行为(尽管只在新式类上):

>>> class StructWithSlots(object):
...     __slots__ = []
...
>>> record = StructWithSlots()
>>> record.number = 3
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'StructWithSlots' object has no attribute 'number'
>>> record.__dict__
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'StructWithSlots' object has no attribute '__dict__'