如何從2個類繼承而不必更改原始類？

Question

每當我運行這段代碼時，我總是得到一個TypeError ，它說__init__() missing 1 required positional argument: 'hours' ，但我並沒有試圖更改ScientificSwimmer類繼承自的原始類的任何內容......如果有道理的話。

這是代碼：

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)

我想要的結果是打印：

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

Answer 1

您的原始類根本沒有正確設計來支持合作繼承，而這正是super的設計目的。 使用super第一條規則是：您不能假設您知道super()將引用哪個類。 這是由self的運行時類型決定的，而不是您靜態繼承的類。

僅使用關鍵字參數以確保方法簽名保持兼容，並始終使用任何未知的關鍵字參數（即簽名中未明確提及的參數super().__init__調用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的方法解析順序是[ScientificSwimmer, Scientist, Swimmer, Human, object] 。 這導致以下結果：

1. ScientificSwimmer不需要定義，因為其他__init__方法會處理一切。
2. Scientist.__init__提取lab關鍵字參數並將其余部分傳遞給下一個類。
3. Swimmer.__init__提取hours關鍵字參數並將其余部分傳遞給下一個類。
4. Human.__init__提取name和age關鍵字參數並將其余部分傳遞給下一個類。
5. object.__init__接收關鍵字參數，所有定義的參數都已被下游類正確提取。