A class is a user-defined blueprint or prototype from which objects are created. Classes provide a means of bundling data and functionality together. Creating a new class creates a new type of object, allowing new instances of that type to be made. Each class instance can have attributes attached to it for maintaining its state. Class instances can also have methods (defined by its class) for modifying its state.
Example:
# 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) |
Output:
COE COE SHIVAM SACHIN 3425 3624 COE
Note: For more information, refer to Python Classes and Objects.
Accessing Parent Class Functions
When a class inherits from another class it inherits the attributes and methods of another class. A class that inherits from another class is known as child class and the class from which the child class inherits is known as Parent class. But have you ever wondered how to access the parent’s class methods? This is really simple, you just have to call the constructor of parent class inside the constructor of child class and then the object of a child class can access the methods and attributes of the parent class.
Example:
# 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() |
Output:
Rahul 886012 30000000
Note: For more information, refer to Inheritance in Python.
Accessing Parent class method from inner class
An inner class or nested class is a defined inside the body of another class. If an object is created using a class, the object inside the root class can be used. A class can have one or more than one inner classes.
Types of Inner Classes:
- Multiple Inner Class
- Multilevel Inner Class
Multiple Inner Class: A class containing more than one inner class.
Example:
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 Codeele = Electronics()ele.laptop.operation()ele.mobile.operation() |
Output:
SINGLA ELECTRONICS DELL Inspiron 15 Redmi Note 5
Multilevel Inner Class: In multilevel inner classes, the inner class contains another class which is inner classes to the previous one.
Example:
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 Codeouter = Vehicle()outer.show_classes()inner = outer.Car()inner.show_classes()innerinner = inner.Maruti() # Calling the method inner_displayinnerinner.inner_display("Just Print It!") |
Output:
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!
