Python Inheritance

Python Inheritance (Python继承)

Understanding Python Inheritance

Understanding Python Inheritance (了解Python继承)

Inheritance is a powerful feature in object-oriented programming that enables the creation of new classes based on existing classes. In Python, inheritance is implemented using the keyword class, which allows a new class to be created as a child or subclass of an existing class. (继承是面向对象编程中的一个强大功能,允许基于现有类创建新类。在Python中,继承是使用关键字class实现的,它允许将新类创建为现有类的子类或子类。)

The Basics of Inheritance

Inheritance enables us to create a new class by inheriting properties from an existing class, known as the parent or base class. The child or derived class inherits all the attributes and methods of the parent class and can also add its own attributes and methods. (继承使我们能够通过从现有类(称为父类或基类)继承属性来创建新类。子类或派生类继承父类的所有属性和方法,也可以添加自己的属性和方法。)

For instance, suppose we have a Vehicle class that has properties such as make, model, and year, and methods such as start and stop. We can create a Car class that inherits from the Vehicle class and adds its own properties such as num_doors and num_seats. The Car class can also override methods such as start and stop if needed. (例如,假设我们有一个Vehicle类,该类具有诸如make、model和year之类的属性,以及诸如start和stop之类的方法。我们可以创建一个Car类,该类继承自Vehicle类,并添加自己的属性,例如num_doors和num_seats。如果需要, Car类还可以覆盖启动和停止等方法。)

Syntax for Inheritance in Python

The syntax for inheritance in Python is straightforward. To create a subclass, we need to specify the name of the parent class in parentheses after the name of the new class. Here’s an example:

class Vehicle:
   def __init__(self, make, model, year):
       self.make = make
       self.model = model
       self.year = year
       
   def start(self):
       print(f"{self.make} {self.model} started.")
       
   def stop(self):
       print(f"{self.make} {self.model} stopped.")

class Car(Vehicle):
   def __init__(self, make, model, year, num_doors, num_seats):
       super().__init__(make, model, year)
       self.num_doors = num_doors
       self.num_seats = num_seats

In this example, the Car class inherits from the Vehicle class using the parentheses notation, and its init method calls the parent class’s init method using the super() function. (在此示例中, Car类使用括号表示法从Vehicle类继承,其__ init 方法使用super ()函数调用父类的 init __方法。)

Overriding Methods

In Python inheritance, a child class can override methods of the parent class if it needs to. This is done by defining a method with the same name in the child class. (在Python继承中,如果需要,子类可以重写父类的方法。这是通过在子类中定义具有相同名称的方法来完成的。)

class Vehicle:
   def __init__(self, make, model, year):
       self.make = make
       self.model = model
       self.year = year
(self.year =年)
       
   def start(self):
       print(f"{self.make} {self.model} started.")
       
   def stop(self):
       print(f"{self.make} {self.model} stopped.")

class Car(Vehicle):
   def start(self):
       print(f"{self.make} {self.model} revved the engine and started.")

In this example, the Car class overrides the start method of the Vehicle class to add a message that the engine is being revved before starting. (在此示例中, Car类重写Vehicle类的start方法,以在启动前添加引擎正在加速的消息。)

Multiple Inheritance

Python also allows multiple inheritance, where a subclass can inherit from multiple parent classes. To do this, we list the parent classes in parentheses, separated by commas. (Python还允许多重继承,其中子类可以从多个父类继承。为此,我们将父类列在括号中,用逗号分隔。)

class Animal:
   def __init__(self, name):
       self.name = name
       
   def speak(self):
       raise NotImplementedError("Subclass must implement abstract method")

class Mammal(Animal):
   def nurse(self):
       pass
   
class Reptile(Animal):
   def lay_eggs(self):
       pass
   
class Platypus(Mammal, Reptile):
   def __init__(self, name):
       super().__init__(name)

In this example, the Platypus class inherits from both the Mammal and Reptile classes, which both inherit from the Animal class. The Platypus class does not need to implement the speak method since it is inherited from the Animal class through its parent classes. (在此示例中,鸭嘴兽类继承自Mammal和Reptile类,这两个类都继承自Animal类。Platypus类不需要实现speak方法,因为它是通过其父类从Animal类继承的。)

Benefits of Inheritance

Inheritance provides several benefits to programmers:

Code Reusability: By inheriting from existing classes, we can reuse code without having to rewrite it. This saves time and reduces the amount of code we need to write.Extensibility: Inheritance enables us to add new functionality to existing classes without modifying their code directly. This helps to keep the code organized and easier to maintain.Polymorphism: Inheritance enables us to create objects that can be treated as instances of their parent or child classes, which allows for more flexible and modular code.

Conclusion

Inheritance is a fundamental concept in object-oriented programming that enables the creation of new classes based on existing classes. Python provides a simple and powerful syntax for implementing inheritance, which allows for code reusability, extensibility, and polymorphism. (继承是面向对象编程中的一个基本概念,它允许基于现有类创建新类。Python为实现继承提供了一个简单而强大的语法,允许代码可重用性、可扩展性和多态性。)

By understanding the basics of inheritance and its benefits, programmers can create more efficient and modular code that can be easily maintained and extended in the future. (通过了解继承的基础知识及其好处,程序员可以创建更高效和模块化的代码,这些代码可以在未来轻松维护和扩展。)



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