Python：为 init 扩展 int 和 MRO

发布于 2024-07-29 02:22:06 字数 600 浏览 2 评论 0原文

在Python中，我试图扩展内置的“int”类型。这样做时，我想将一些关键字参数传递给构造函数，因此我这样做：

class C(int):
     def __init__(self, val, **kwargs):
         super(C, self).__init__(val)
         # Do something with kwargs here...

但是，在调用 C(3) 时工作正常，C(3, a=4) code> 给出：

'a' is an invalid keyword argument for this function`

并且 C.__mro__ 返回预期的：

(<class '__main__.C'>, <type 'int'>, <type 'object'>)

但似乎 Python 试图首先调用 int.__init__...有人知道为什么吗？这是解释器中的错误吗？

原文

In Python, I'm trying to extend the builtin 'int' type. In doing so I want to pass in some keywoard arguments to the constructor, so I do this:

class C(int):
     def __init__(self, val, **kwargs):
         super(C, self).__init__(val)
         # Do something with kwargs here...

However while calling C(3) works fine, C(3, a=4) gives:

'a' is an invalid keyword argument for this function`

and C.__mro__ returns the expected:

(<class '__main__.C'>, <type 'int'>, <type 'object'>)

But it seems that Python is trying to call int.__init__ first... Anyone know why? Is this a bug in the interpreter?

分享到QQ

分享到微博

如果你对这篇内容有疑问，欢迎到本站社区发帖提问参与讨论，获取更多帮助，或者扫码二维码加入 Web 技术交流群。

发布评论

需要登录才能够评论，你可以免费注册一个本站的账号。

那些过往 2024-08-05 02:22:06

Python 数据模型的文档建议使用 __new__：

object .新(cls[, ...])

new() 主要旨在允许不可变类型（如 int、str 或 tuple）的子类自定义实例创建。为了自定义类创建，它通常在自定义元类中被重写。

对于您给出的示例，应该执行类似的操作：

class C(int):

    def __new__(cls, val, **kwargs):
        inst = super(C, cls).__new__(cls, val)
        inst.a = kwargs.get('a', 0)
        return inst

The docs for the Python data model advise using __new__:

object.new(cls[, ...])

new() is intended mainly to allow subclasses of immutable types (like int, str, or tuple) to customize instance creation. It is also commonly overridden in custom metaclasses in order to customize class creation.

Something like this should do it for the example you gave:

class C(int):

    def __new__(cls, val, **kwargs):
        inst = super(C, cls).__new__(cls, val)
        inst.a = kwargs.get('a', 0)
        return inst

回复收藏 0 原文