什么时候调用 Python 的 super().__init__()?

问题描述

(在谷歌搜索后，我无法在任何地方找到有关此问题的参考.)

(I am unable to find a reference anywhere on this matter after some Googling.)

这个简短的代码示例可以清楚地展示这个场景:

The scenario can be clearly demonstrated with this short code sample:

class X:
    def __init__(self, stuff):
        self.__stuff = stuff

class Y(X):
    def __init__(self, stuff):
        # Is it safe to execute statements before calling super.__init__()?
        new_stuff = self.call_another_method(stuff)
        super(Y, self).__init__(new_stuff)

使用 CPython 3.x，上述代码示例有效——假设 call_another_method() 存在.这种编码风格通常是安全的，但不喜欢或被认为是非 Pythonic 的?我无法找到有关此问题的建议.

Using CPython 3.x, the above code sample works -- assuming call_another_method() exists. It this coding style generally safe, but frowned upon or considered unPythonic? I am unable to find advice on this matter.

我为什么在乎?

我的背景来自更传统的面向对象编程语言，例如 C++、C# 和 Java，其中必须严格调用super"作为子类构造函数中的第一条语句——忽略零参数、隐式大小写.

My background comes from more traditional object oriented programming languages such as C++, C#, and Java where "super" must be called strictly as the first statement in a subclass constructor -- ignoring the zero-argument, implicit case.

如果重要的话，我是一个年轻的 Pythoneer:3+，拜托了.

If it matters, I am a young Pythoneer: 3+, please.

推荐答案

是的，在 super() 之前调用其他东西是完全安全的.Python 不设置顺序，并且有很多用例.

Yes, it is perfectly safe to call other things before super(). Python doesn't set an order, and there are plenty of use-cases for this.

请注意，super().__init__() 调用只是 Python 中的另一个表达式，它不是语法结构.例如，您也可以在方法之外使用 super()，前提是您传入正确的参数.

Note that super().__init__() call is just another expression in Python, it is not a syntax construct. You can use super() outside methods too, for example, provided you pass in the right arguments.

在您的情况下，您可以省略类型和实例参数，当 super() 不带参数调用时，Python 3 会为您检索这些参数，因为您在内部定义的函数中使用它班级:

In your case, you can omit the type and instance arguments, Python 3 will retrieve these for you when super() is called without arguments, because you are using it in a function defined inside a class:

class Y(X):
    def __init__(self, stuff):
        new_stuff = self.call_another_method(stuff)
        # super(Y, self) is implicit here:
        super().__init__(new_stuff)

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