通过子类化修改命名元组的构造函数参数？

发布于 2024-09-14 00:50:48 字数 649 浏览 11 评论 0原文

我想创建一个 namedtuple 来表示短位字段中的各个标志。我正在尝试对其进行子类化，以便可以在创建元组之前解压位字段。但是，我当前的尝试不起作用：

class Status(collections.namedtuple("Status", "started checking start_after_check checked error paused queued loaded")):
    __slots__ = ()

    def __new__(cls, status):
        super(cls).__new__(cls, status & 1, status & 2, status & 4, status & 8, status & 16, status & 32, status & 64, status & 128)

现在，我对 super() 的经验有限，并且我对 __new__ 的经验几乎不存在，所以我不非常确定（对我来说）神秘错误 TypeError: super.__new__(Status): Status is not a subtype of super 的含义。谷歌搜索和深入研究文档并没有产生任何启发性的东西。

帮助？

原文

I want to create a namedtuple which represents the individual flags in a short bitfield. I'm trying to subclass it so that I can unpack the bitfield before the tuple is created. However, my current attempt isn't working:

class Status(collections.namedtuple("Status", "started checking start_after_check checked error paused queued loaded")):
    __slots__ = ()

    def __new__(cls, status):
        super(cls).__new__(cls, status & 1, status & 2, status & 4, status & 8, status & 16, status & 32, status & 64, status & 128)

Now, my experience with super() is limited and my experience with __new__ is virtually non-existent, so I'm not quite sure what to make of the (to me) enigmatic error TypeError: super.__new__(Status): Status is not a subtype of super. Googling and digging into the docs haven't yielded anything enlightening.

Help?

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噩梦成真你也成魔 2024-09-21 00:50:49

你几乎已经成功了 :-) 只有两个小修正：

new 方法需要一个 return 语句
super 调用应该有两个参数， cls 和 Status

结果代码如下所示：

import collections

class Status(collections.namedtuple("Status", "started checking start_after_check checked error paused queued loaded")):
    __slots__ = ()

    def __new__(cls, status):
        return super(cls, Status).__new__(cls, status & 1, status & 2, status & 4, status & 8, status & 16, status & 32, status & 64, status & 128)

它运行干净，就像您所期望的那样：

>>> print Status(47)
Status(started=1, checking=2, start_after_check=4, checked=8, error=0, paused=32, queued=0, loaded=0)

You almost had it :-) There are just two little corrections:

The new method needs a return statement
The super call should have two arguments, cls and Status

The resulting code looks like this:

import collections

class Status(collections.namedtuple("Status", "started checking start_after_check checked error paused queued loaded")):
    __slots__ = ()

    def __new__(cls, status):
        return super(cls, Status).__new__(cls, status & 1, status & 2, status & 4, status & 8, status & 16, status & 32, status & 64, status & 128)

It runs cleanly, just like you had expected:

>>> print Status(47)
Status(started=1, checking=2, start_after_check=4, checked=8, error=0, paused=32, queued=0, loaded=0)

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旧梦荧光笔 2024-09-21 00:50:49

我会避免使用 super 除非你明确地迎合多重继承（希望不是这里的情况；-）。只需做一些像...：

def __new__(cls, status):
    return cls.__bases__[0].__new__(cls,
                                    status & 1, status & 2, status & 4,
                                    status & 8, status & 16, status & 32,
                                    status & 64, status & 128)

I'd avoid super unless you're explicitly catering to multiple inheritance (hopefully not the case here;-). Just do something like...:

def __new__(cls, status):
    return cls.__bases__[0].__new__(cls,
                                    status & 1, status & 2, status & 4,
                                    status & 8, status & 16, status & 32,
                                    status & 64, status & 128)

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