`object.__setattr__(self, ..., ...)` 而不是 `setattr(self, ..., ...)`? [英] `object.__setattr__(self, ..., ...)` instead of `setattr(self, ..., ...)`?

问题描述

以下是 werkzeug 库中 Local 类的 __init__ 方法:

Following is the __init__ method of the Local class from the werkzeug library:

def __init__(self):
    object.__setattr__(self, '__storage__', {})
    object.__setattr__(self, '__ident_func__', get_ident)

我不明白这段代码的两件事:

I don't understand two things about this code:

1. 他们为什么写

1. Why did they write

object.__setattr__(self, '__storage__', {})

而不仅仅是

`setattr(self, '__storage__', {})`

如果可以简单地写，他们为什么还要使用 __setattr__

self.__storage__ = {}

推荐答案

这确保使用 __setattr__ 的默认 Python 定义.如果类已覆盖 __setattr__ 以执行非标准行为，但您仍希望访问原始 __setattr__ 行为，则通常使用它.

This ensures that the default Python definition of __setattr__ is used. It's generally used if the class has overridden __setattr__ to perform non-standard behaviour, but you still wish to access the original __setattr__ behaviour.

对于werkzeug，如果您查看Local 类，您会看到__setattr__ 的定义如下:

In the case of werkzeug, if you look at the Local class you'll see __setattr__ is defined like this:

def __setattr__(self, name, value):
    ident = self.__ident_func__()
    storage = self.__storage__
    try:
        storage[ident][name] = value
    except KeyError:
        storage[ident] = {name: value}

不是在对象的字典中设置属性，而是在之前初始化的 __storage__ 字典中设置它们.为了完全设置 __storage__ 属性(以便以后可以像 self.__storage__ 一样访问它)，__setattr__ 的原始定义来自必须使用对象，这就是为什么在构造函数中使用笨拙的符号.

Instead of setting attributes in the dictionary of the object, it sets them in the __storage__ dictionary that was initialized previously. In order to set the __storage__ attribute at all (so that it may be accessed like self.__storage__ later), the original definition of __setattr__ from object must be used, which is why the awkward notation is used in the constructor.

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