继承类；如何实施

Question

我在类中继承和插入数据有错吗？

class Car:
    def __init__(self, make, model, year):
        self.make = "Honda"
        self.model = "Minivan"
        self.year = "2010"

class Entry(Car):
    def __init__(self, make, model, year, driver, number):
        super().__init__(make, model, year)
        self.driver = "Mike Drosser"
        self.number = 9
    def printEntry(self):
        print("The make is: "+self.make)
        print("The model is: "+self.model)
        print("The year is: "+self.year)

        print("The driver is: "+self.driver)
        self.number = str(self.number)
        print("The number is: "+self.number)

x = Entry()
x.printEntry()

我必须单独提交Car类数据吗？

Answer 1

您的代码有 2 个问题：

1. 构造函数中的参数都是必需的，因此在执行Entry() 时会失败，因为没有提供任何参数。

2. 您不会对构造函数提供的值做任何事情，而是将特定值存储在您的实例属性中。

除此之外，其他一切看起来都很好。

一个简单的解决方法是

class Car:

    def __init__(self, make, model, year):
        self.make = make #we store the provided value
        self.model = model
        self.year = year

class Entry(Car):

    def __init__(self, make, model, year, driver, number):
        super().__init__(make, model, year)
        self.driver = driver
        self.number = number
        
    def printEntry(self):
        print("The make is: "+self.make)
        print("The model is: "+self.model)
        print("The year is: "+self.year)

        print("The driver is: "+self.driver)
        self.number = str(self.number)
        print("The number is: "+self.number)

x = Entry("Honda", "Minivan", "2010", "Mike Drosser", 9) #this is how a proper call of this class would look like
x.printEntry()

还有其他可以改变的东西，比如你的打印，打印函数可以接受任意数量的参数，所以这个print("The number is: "+self.number)可以更改为print("The number is:", self.number)这样你就不需要显式转换它如果是数字或任何非字符串，则首先转换为字符串。

但是为了更加pythonic，把printEntry方法改成__str__这个特殊方法，这样就可以在里面调用print了

class Car:

    def __init__(self, make, model, year):
        self.make = make
        self.model = model
        self.year = year
        
    def __str__(self):
        #this method should return a string representation of this class, 
        #for this we use f-string to format the different attributes
        return f"The make is: {self.make}\nThe model is: {self.model}\nThe year is: {self.year}"

class Entry(Car):

    def __init__(self, make, model, year, driver, number):
        super().__init__(make, model, year)
        self.driver = driver
        self.number = number
        
    def __str__(self):
        #here we make use of inheritances to split job 
        #by letting the Car class handle the part it 
        #know about and this subclass will add to it 
        #with the part exclusive to it
        return super().__str__() + f"\nThe driver is: {self.driver}\nThe number is: {self.number}"
        
        

x = Entry("Honda", "Minivan", "2010", "Mike Drosser", 9)
print(x)