派生类构造函数在python中如何工作？

Question

我有以下基类：

class NeuralNetworkBase:
    def __init__(self, numberOfInputs, numberOfHiddenNeurons, numberOfOutputs):
        self.inputLayer = numpy.zeros(shape = (numberOfInputs))
        self.hiddenLayer = numpy.zeros(shape = (numberOfHiddenNeurons))
        self.outputLayer = numpy.zeros(shape = (numberOfOutputs))

        self.hiddenLayerWeights = numpy.zeros(shape = (numberOfInputs, numberOfHiddenNeurons))
        self.outputLayerWeights = numpy.zeros(shape = (numberOfHiddenNeurons, numberOfOutputs))

现在，我有一个派生类，代码如下：

class NeuralNetworkBackPropagation(NeuralNetworkBase):
    def __init__(self, numberOfInputs, numberOfHiddenNeurons, numberOfOutputs):
        self.outputLayerDeltas = numpy.zeros(shape = (numberOfOutputs))
        self.hiddenLayerDeltas = numpy.zeros(shape = (numberOfHiddenNeurons))

但当我实例化NeuralNetworkBackPropagation时，我希望两个构造函数都被调用，也就是说，我不想重写基类的构造函数。在运行派生类“one”时，python是否默认调用基类构造函数？我必须隐式地在派生类构造函数中进行吗？

Answer 1

您必须将其放入NeuralNetworkBackPropagation的__init__()方法中，即调用父类（NeuralNetworkBase）的__init__()方法：

NeuralNetworkBase.__init__(self, numberOfInputs, numberOfHiddenNeurons, numberOfOutputs)

父类的构造函数总是自动调用的，除非您在子类中覆盖它。如果您在子类中覆盖它，并且还想调用父类的类构造函数，那么您必须按照我上面所示的那样执行。

Answer 2

Does python call by default the base class constructor's when running the derived class' one? Do I have to implicitly do it inside the derived class constructor?

不，是的。

这与Python处理其他被重写方法的方式是一致的，如果希望在继承类中使用该功能，则必须显式调用基类中被重写的任何方法。

你的构造器应该是这样的：

def __init__(self, numberOfInputs, numberOfHiddenNeurons, numberOfOutputs):
    NeuralNetworkBase.__init__(self, numberOfInputers, numberOfHiddenNeurons, numberOfOutputs)
    self.outputLayerDeltas = numpy.zeros(shape = (numberOfOutputs))
    self.hiddenLayerDeltas = numpy.zeros(shape = (numberOfHiddenNeurons))

或者，可以使用Python的^{}函数来实现相同的功能，但是you need to be careful when using it。