所有 Python 类都应该扩展对象吗? [英] Should all Python classes extend object?

问题描述

我发现以下两种方法都有效:

class Foo():定义一个(自我):打印你好"类 Foo(对象):定义一个(自我):打印你好"

所有 Python 类都应该扩展对象吗?不扩展对象有什么潜在的问题吗?

解决方案

在 Python 2 中，不从 object 继承将创建一个旧式的类，除其他效果外，它会导致 输入给出不同的结果:

<预><代码>>>>Foo类:通过...>>>类型(Foo())<输入实例">

对比

<预><代码>>>>类 Bar(object): 通过...>>>类型(酒吧())<class '__main__.Bar'>

多重继承的规则也是不同的，我什至不会试着在这里总结一下.我见过的所有关于 MI 的优秀文档都描述了新式类.

最后，旧式类在 Python 3 中消失了，从 object 继承变得隐含.所以，除非你需要向后兼容旧软件，否则总是喜欢新风格的类.

I have found that both of the following work:

class Foo():
    def a(self):
        print "hello"

class Foo(object):
    def a(self):
        print "hello"

Should all Python classes extend object? Are there any potential problems with not extending object?

解决方案

In Python 2, not inheriting from object will create an old-style class, which, amongst other effects, causes type to give different results:

>>> class Foo: pass
... 
>>> type(Foo())
<type 'instance'>

vs.

>>> class Bar(object): pass
... 
>>> type(Bar())
<class '__main__.Bar'>

Also the rules for multiple inheritance are different in ways that I won't even try to summarize here. All good documentation that I've seen about MI describes new-style classes.

Finally, old-style classes have disappeared in Python 3, and inheritance from object has become implicit. So, always prefer new style classes unless you need backward compat with old software.

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