python - 如何在python中更改对象的类型

Question

来自 pydocs

Like its identity, an object’s type is also unchangeable. [1]

来自 footnote

It is possible in some cases to change an object’s type, under certain controlled conditions. It generally isn’t a good idea though, since it can lead to some very strange behaviour if it is handled incorrectly.

什么情况下我们可以改变对象的类型以及如何改变它

Answer 1

class A:
    pass

class B:
    pass

a = A()

isinstance(a, A)  # True
isinstance(a, B)  # False
a.__class__  # __main__.A

# changing the class
a.__class__ = B

isinstance(a, A)  # False
isinstance(a, B)  # True
a.__class__  # __main__.B

但是，我不记得它可以提供帮助的真实示例。通常，类操作是在创建类(不是类的对象)时由装饰器或元类完成的。例如， dataclasses.dataclass是一个装饰器，它接受一个类并在它的基础上构造另一个类(参见 the source code)。