如何从2个类继承而不必更改原始类？

Question

每当我运行这段代码时，我总是得到一个TypeError，上面写着__init__() missing 1 required positional argument: 'hours'， 但是我没有试图改变ScientificSwimmer类继承自的原始类的任何内容……如果这有意义的话

代码如下：

class Human:
    def __init__(self, name, age):
        self.name = name
        self.age = age

    def hobby(self):
        print("Likes watching Netflix")

    def info(self):
        print(self.name , "is ",self.age," years old")


class Scientist(Human):
    def __init__(self, name, age, lab):
        super().__init__(name, age)
        self.lab = lab

    def hobby(self):
        print("Likes doing scientific experiments")

    def labName(self,lab):
        print("works at the " ,lab, "laboratory")


class Swimmer(Human):
    def __init__(self, name, age, hours):
        super().__init__(name,age)
        self.hours = hours

    def hobby(self):
        print("likes swimmming in the lake" )

    def hoursSwimming(self, hours):
        print("swims ", hours , "hours per week")


class ScientificSwimmer(Scientist, Swimmer):

    def __init__ (self, name, age, lab, hours):
       Scientist.__init__(self,name, age, lab)
       Swimmer.__init__(self, name, age, hours)


scienswim = ScientificSwimmer("\nJohn Smith", 30, "nuclear", 100)
scienswim.info()
scienswim.hobby()
scienswim.labName("nuclear")
scienswim.hoursSwimming(100)

我想要的结果是打印：

John smith is 30 years old.
likes doing scientific experiments.
works at the nuclear laboratory.
swims 100 hours per week.

Answer 1

您的原始类根本没有正确地设计为支持协作继承，这就是super的设计目的。使用super的第一条规则是：不能假设您知道super()将引用哪个类。这是由self的运行时类型决定的，而不是静态继承自的类

只使用关键字参数以确保方法签名保持兼容，并始终使用任何未知关键字参数（即签名中未明确提及的参数）调用super().__init__

class Human: 
    def __init__(self, *, name, age, **kwargs):
        super().__init__(**kwargs)
        self.name = name
        self.age = age
        
    def hobby(self):
        print("Likes watching Netflix")
        
    def info(self):
        print(self.name , "is ",self.age," years old")
        

class Scientist(Human): 
    def __init__(self, *, lab, **kwargs):
        super().__init__(**kwargs)
        self.lab = lab
        
    def hobby(self):
        print("Likes doing scientific experiments")
    
    def labName(self):
        print("works at the " , self.lab, "laboratory")
  

class Swimmer(Human):
    def __init__(self, *, hours, **kwargs):
        super().__init__(**kwargs)
        self.hours = hours
    
    def hobby(self):
        print("likes swimmming in the lake" )
    
    def hoursSwimming(self):
        print("swims ", self.hours , "hours per week")
     

class ScientificSwimmer(Scientist, Swimmer):
    pass


scienswim = ScientificSwimmer(name="John Smith", age=30, lab="nuclear", hours=100)
scienswim.info()
scienswim.hobby()
scienswim.labName()
scienswim.hoursSwimming()

ScientificSwimmer的方法解析顺序为[ScientificSwimmer, Scientist, Swimmer, Human, object]。其结果如下：

1. ScientificSwimmer不需要定义，因为其他{}方法将处理所有事情
2. Scientist.__init__提取lab关键字参数，并将其余参数传递给下一个类
3. Swimmer.__init__提取hours关键字参数，并将其余参数传递给下一个类
4. Human.__init__提取name和age关键字参数，并将其余参数传递给下一个类
5. object.__init__未接收任何关键字参数，下游类已正确提取所有定义的参数