Class Objects in Python

Python class

Class is a blueprint or Skelton.

Which gives information about how will be the class object.

Some of the class examples are Fruit, Human, Cars.

Object structure will be the same as class structure.

Python Object

The real-world entity is called object, object has property and behaviour.

Real-world entity means things which exist in real forms.

some examples are Apple, Men, BMW car.

all these entities exist in real-world with some kind of properties and behaviour.

property and behaviour of an object define or gives information about object that which kind of object is this.

Declaration of class in python

Syntax

class Class_name:

        member variable

        member methods

Example

class Person:
    name=""
    def set_name(self):
        self.name="Aman"

Creating a new object of the class in python

Syntax

object_name=Class_name()

Example

obj=Person()

Accessing a member of a class

Accessing member (member variable, member methods) of a class means to access(set or get ) value of member variable and methods.

Member variable can be accessed inside or outside of class.

Accessing member variable and methods inside of a class

class Person:
    name=""

    def set_name(self):
        self.name="Aman"   # accessing member variable

    def print_name(self):
        self.set_name() # accessing member method
        print(self.name) # accessing member variable

p=Person()
p.print_name()

Accessing member variable and method outside of a class

class Person:
    name=""

    def print_name(self):        
        print(self.name)

p=Person()
p.name="John" # accessing member variable of a class
p.print_name() # accessing member methods of a class

Self keyword in a python class

self keyword is a current class object, it is same as java this keyword which point to current class as an object.

when you are accessing member variables and methods inside a class, it is mandatory to use of a self keyword.

class Person:
    name=""

    def set_name(self): # current class object pointer
        self.name="Aman" # accessing member variable of a class using self keyword

    def print_name(self):
        self.set_name() # accessing member methods of a class using self keyword
        print(self.name)

p=Person()
p.print_name()

Parametrized function in a python class

class Calculator:
    x=0
    y=0
    z=0

    def add(self, first_number, second_number):
        self.x=first_number
        self.y=second_number
        self.z=self.x+self.y
        print("sum:",self.z)

    def sub(self, first_number, second_number):
        self.x=first_number
        self.y=second_number
        self.z=self.x-self.y
        print("Subtract:",self.z)

c=Calculator()
c.add(10,20)
c.sub(20,10)

the return statement in class methods in a python

As we already learned at the python function tutorial about the return statement, the return statements also can be used within class methods.

class Calculator:
    x=0
    y=0
    z=0

    def add(self, first_number, second_number):
        self.x=first_number
        self.y=second_number
        self.z=self.x+self.y
        return self.z

    def sub(self, first_number, second_number):
        self.x=first_number
        self.y=second_number
        self.z=self.x-self.y
        return self.z

c=Calculator()

x=c.add(10,20)
print("sum:",x)

y=c.sub(20,10)
print("subtract:",y)