在Python中声明一个带有类实例的类 [英] Declaring a class with an instance of it inside in Python

问题描述

也许标题有点搞砸了，但是有没有办法在Python的同一类中创建类的实例？

Maybe the title is a little screwed up but is there a way to make an instance of a class inside the same class in Python?

类似这样的东西：

class Foo:
    foo = Foo()

我知道口译员说Foo没有声明，但是有办法实现吗？

I know that the interpreter says that Foo is not declared but is there a way to achieve this?

更新：

这就是我要执行的操作：

This is what I'm trying to do:

class NPByteRange (Structure): 
    _fields_ = [ ('offset', int32), 
                 ('lenght', uint32), 
                 ('next', POINTER(NPByteRange)) ]

推荐答案

解释器只会介意尝试在未声明 Foo 的情况下执行此操作。在某些情况下是存在的。最简单的示例在方法中：

The interpreter only minds if you try to do it in a context where Foo is not declared. There are contexts where it is. The simplest example is in a method:

>>> class Beer(object):
...   def have_another(self):
...     return Beer()
... 
>>> x=Beer()
>>> x.have_another()
<__main__.Beer object at 0x10052e390>

如果将对象作为属性很重要，则可以使用

If its important that the object be a property, you can just use the property builtin.

>>> class Beer(object):
...   @property
...   def another(self):
...     return Beer()
... 
>>> guinness=Beer()
>>> guinness.another
<__main__.Beer object at 0x10052e610>

最后，如果确实有必要将其作为 class 属性， ，您也可以这样做。

Finally, if it's truly necessary that it be a class property, well, you can do that, too.

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