将类“对象"分类为子类的目的是什么?在Python中? [英] What is the purpose of subclassing the class "object" in Python?

问题描述

所有Python内置都是object的子类，我也遇到了许多用户定义的类.为什么?类object的目的是什么?这只是一个空的课，对吧?

All the Python built-ins are subclasses of object and I come across many user-defined classes which are too. Why? What is the purpose of the class object? It's just an empty class, right?

推荐答案

简而言之，它设置了免费的魔法小马.

In short, it sets free magical ponies.

长期以来，Python 2.2和更早版本使用旧样式类".它们是类的特定实现，并且有一些限制(例如，您不能对内置类型进行子类化).解决此问题的方法是创建一种新的类样式.但是，这样做将涉及一些向后不兼容的更改.因此，为确保为旧样式类编写的代码仍然有效，创建了object类以充当所有新样式类的超类. 因此，在Python 2.X中，class Foo: pass将创建一个旧样式类，而class Foo(object): pass将创建一个新样式类.

In long, Python 2.2 and earlier used "old style classes". They were a particular implementation of classes, and they had a few limitations (for example, you couldn't subclass builtin types). The fix for this was to create a new style of class. But, doing this would involve some backwards-incompatible changes. So, to make sure that code which is written for old style classes will still work, the object class was created to act as a superclass for all new-style classes. So, in Python 2.X, class Foo: pass will create an old-style class and class Foo(object): pass will create a new style class.

详细内容请参见Guido的> 在Python 2.2中统一类型和类 .

In longer, see Guido's Unifying types and classes in Python 2.2.

而且，通常，养成使所有类成为新样式的习惯是个好主意，因为有些事情(@property装饰器是我想到的)不会与旧样式一起使用课.

And, in general, it's a good idea to get into the habit of making all your classes new-style, because some things (the @property decorator is one that comes to mind) won't work with old-style classes.

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