如何从 Python 中的子类调用和覆盖父类方法

Question

在reproduce方法ResistantVirus类，我试图调用reproduce(self, popDensity)的SimpleVirus类，但而不是返回SimpleVirus的对象，我希望它返回一个ResistantVirus对象。

显然，我也可以从SimpleVirus.reproduce方法中重复一些代码并在我的ResistantVirus.reproduce方法中使用相同的实现，但我想知道是否可以调用和覆盖SimpleVirus.reproduce以避免重复？

class SimpleVirus(object):

    def __init__(self, maxBirthProb, clearProb):
        self.maxBirthProb = maxBirthProb
        self.clearProb = clearProb

    def reproduce(self, popDensity):
        if random.random() > self.maxBirthProb * (1 - popDensity):
            raise NoChildException('In reproduce()')
        return SimpleVirus(self.getMaxBirthProb(), self.getClearProb())


class ResistantVirus(SimpleVirus):

    def __init__(self, maxBirthProb, clearProb, resistances, mutProb):
        SimpleVirus.__init__(self, maxBirthProb, clearProb)
        self.resistances = resistances
        self.mutProb = mutProb

    def reproduce(self, popDensity)       

      ## returns a new instance of the ResistantVirus class representing the       
      ## offspring of this virus particle. The child should have the same   
      ## maxBirthProb and clearProb values as this virus.

      ## what I sketched out so far and probs has some mistakes:
      for drug in activeDrugs:
          if not self.isResistantTo(drug):
              raise NoChildException
              break

      simple_virus = SimpleVirus.reproduce(self,popDensity)

      return ResistantVirus(simple_virus.getMaxBirthProb(),simple_virus.getClearProb())

Answer 1

只要__init__()签名兼容，您就可以使用实例的类型而不是显式类型。

class Parent(object):
    def __str__(self):
        return 'I am a Parent'

    def reproduce(self):
        # do stuff common to all subclasses.
        print('parent reproduction')
        # then return an instance of the caller's type
        return type(self)()

class Child(Parent):
    def __str__(self):
        return 'I am a Child'

    def reproduce(self):
        # do stuff specific to Child.
        print('child reproduction')
        # call the parent's method but it will return a
        # Child object
        return super(Child, self).reproduce()


print(Parent().reproduce())

parent reproduction    
I am a Parent

print(Child().reproduce())

child reproduction
parent reproduction
I am a child