Classes in Python

In this tutorial we are going to learn :

Classes in Python
Creating A Class
Constructors
Private Members

Classes in Python

Python is an object-oriented programming language. Almost everything in Python is an object.

Important concepts :

Class : helps us to create an object and it is simply a blueprint of an object.
Object : an instance of a class.
Method : A function which is created in the class.
Attributes : A variable bound to an instance of a class.

Let’s give an example Class and Object

Class : Animal
Object : Cat, Dog, Bird.

Creating A Class

We use the class keyword to create a class.

Note :

Class name rule : First letter of each internal word should be upper case.

Example:

class MyClass:          # creating a class
    def person(self):
        print("Hello")
        

my_class = MyClass()    # creating an object called my_class
my_class.person()

Constructors

The example programs above are classes and objects in their simplest form. To understand the meaning of classes we have to understand the constructors ( __init__ function ) .

All classes have __init__ function and it is always executed when the class is being
initiated.

Example :

As you can see when we create a constructor and create variables we can access his variables from outside.

the self parameter is a reference to the current instance of the object. So we can access the variables.

Example :

class MyClass:
    def __init__(self, first, second):
        self.first = first
        self.second = second


my_class = MyClass(1,2)
print(my_class.first)

Example :

The self parameter is a reference to the current instance of the class and we use to access variables that belong to the class.

class MyClass:
    def __init__(self, first, second):
        self.first = first
        self.second = second

    def number(self):
        print(f"First Number {self.first}, Second Number {self.second}")


my_class = MyClass(1, 2)
my_class.number()

Private Members

To make our variables private, we use double underscores ( __ ) .

Example :

As you can see we can’t access our private name variable and our program raise an error.