Python – 访问父类属性

类是用户定义的蓝图或原型，从中创建对象。类提供了一种将数据和功能捆绑在一起的方法。创建一个新类会创建一种新类型的对象，允许创建该类型的新实例。每个类实例都可以附加属性以维护其状态。类实例也可以具有用于修改其状态的方法（由其类定义）。

例子：

# Python program to demonstrate
# classes and objects
  
  
# Creating a class 
class Student:
      
    # Class Variable
    stream = 'COE'
      
    def __init__(self, name, roll_no):
  
        # Instance Variable
        self.name = name 
        self.roll_no = roll_no 
  
# Objects of Student class 
a = Student('SHIVAM', 3425) 
b = Student('SACHIN', 3624)
  
print(a.stream)
print(b.stream)
print(a.name)
print(b.name)
print(a.roll_no) 
print(b.roll_no)
  
# Class variables can be 
# accessed using class 
# name also 
print(Student.stream)

输出：

COE
COE
SHIVAM
SACHIN
3425
3624
COE

注意：有关详细信息，请参阅Python类和对象。

访问父类函数

当一个类从另一个类继承时，它会继承另一个类的属性和方法。从另一个类继承的类称为子类，子类继承的类称为父类。但是你有没有想过如何访问父类的类方法？这很简单，你只需要在子类的构造函数中调用父类的构造函数，然后子类的对象就可以访问父类的方法和属性。

例子：

# Python code to demonstrate 
# how parent constructors are called. 
    
# parent class 
class Person( object ):     
    
        # __init__ is known as the constructor          
        def __init__(self, name, idnumber):    
                self.name = name 
                self.idnumber = idnumber 
                  
        def display(self): 
                print(self.name) 
                print(self.idnumber) 
    
# child class 
class Employee( Person ):            
        def __init__(self, name, idnumber, salary): 
                self.salary = salary 
    
                # invoking the constructor of 
                # the parent class  
                Person.__init__(self, name, idnumber)  
          
        def show(self):
            print(self.salary)
    
                    
# creation of an object
# variable or an instance 
a = Employee('Rahul', 886012, 30000000)     
    
# calling a function of the
# class Person using Employee's
# class instance 
a.display()
a.show() 

输出：

Rahul
886012
30000000

注意：有关更多信息，请参阅Python中的继承。

从内部类访问父类方法

内部类或嵌套类是在另一个类的主体内定义的。如果使用类创建对象，则可以使用根类中的对象。一个类可以有一个或多个内部类。

内部类的类型：

• 多个内部类
• 多级内部类

多个内部类：包含多个内部类的类。

例子：

class Electronics:
    def __init__(self):
        print('SINGLA ELECTRONICS')
        self.laptop=self.Laptop()
        self.mobile=self.Mobile()
          
    # Inner Class 1
    class Laptop:
        def operation(self):
            print('DELL Inspiron 15')
              
    # Inner Class 2
    class Mobile:
        def operation(self):
            print('Redmi Note 5')
              
# Driver Code
ele = Electronics()
ele.laptop.operation()
ele.mobile.operation()

输出：

SINGLA ELECTRONICS
DELL Inspiron 15
Redmi Note 5

多级内部类：在多级内部类中，内部类包含另一个类，该类是前一个内部类。

例子：

class Vehicle:
  
    def __init__(self):
          
        # instantiating the 'Inner' class
        self.inner = self.Car()
          
        # instantiating the multilevel
        # 'InnerInner' class
        self.innerinner = self.inner.Maruti()
  
    def show_classes(self):
        print("This is in Outer class that is Vehicle")
          
  
    # inner class
    class Car:
        # First Inner Class
  
        def __init__(self):
              
            # instantiating the 
            # 'InnerInner' class
            self.innerinner = self.Maruti()
              
        def show_classes(self):
            print("This is in Inner class that is Car")
              
        # multilevel inner class
        class Maruti:
  
            def inner_display(self, msg):
                print("This is in multilevel InnerInner\
                      class that is Maruti")
                print(msg)
  
      
# Driver Code
outer = Vehicle()
outer.show_classes()
inner = outer.Car()
inner.show_classes()
innerinner = inner.Maruti()
  
# Calling the method inner_display
innerinner.inner_display("Just Print It!")

输出：

This is in Outer class that is Vehicle
This is in Inner class that is Car
This is in multilevel InnerInner class that is Maruti
Just Print It!