类声明之间的区别 [英] Difference between class declarations

问题描述

我看到一些类似的问题，但我想确定，所以我问...

I see some similar questions about this topic, but i wish to be sure, so i am asking...

有什么区别：

class MyClass:
    pass

和

class MyClass():
    pass

此外，这两者之间是否有区别：

Also, is there a difference between these two:

class MyClass():
    pass

class MyClass(object):
    pass

推荐答案

前两个拼写没有区别。

python 2.7，在后两个之间有一个巨大的区别。继承对象使其成为 new-style类，改变继承语义并添加对描述符的支持（ @property ， @classmethod ，等等）。这是Python 3中的默认值。

In python 2.7, there is a huge difference between the latter two. Inheriting from object makes it a new-style class, changing the inheritance semantics and adding support for descriptors (@property, @classmethod, etc.). It's the default in Python 3.

在Python 2.2中引入了新式类来统一类型（例如 int 和 list ）和类，并且因为一些事情以向后不兼容的方式发生变化，所以需要'opt in'，显式继承 object

New-style classes were introduced in Python 2.2 to unify types (such as int and list), and classes, and because several things change in backwards-incompatible ways, you need to 'opt in', explicitly inherit from object to enable the changes.

在Python 3中，继承自 object 需要，课程是新式的，总是。

In Python 3, inheriting from object is no longer needed, classes are new-style, always.

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