Python Object and Classes

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Creating object and classes

Python is an object-oriented language. In python everything is object i.e int , str , bool  even modules, functions are also objects.

Object oriented programming use objects to create programs, and these objects stores data and behaviors.

Defining class

Class name in python is preceded with class  keyword followed by colon ( : ). Classes commonly contains data field to store the data and methods for defining behaviors. Also every class in python contains a special method called initializer (also commonly known as constructors), which get invoked automatically every time new object is created.

Let’s see an example.

 

here we have created a class called Person  which contains one data field called name  and method whoami().

What is self ??

All methods in python including some special methods like initializer have first parameter self . This parameter refers to the object which invokes the method. When you create new object the self parameter in the __init__  method is automatically set to reference the object you have just created.

Creating object from class


Expected Output
:

Note: When you call a method you don’t need to pass anything to self  parameter, python automatically does that for you behind the scenes.

You can also change the name  data field.

Expected Output:

Although it is a bad practice to give access to your data fields outside the class. We will discuss how to prevent this next.

Hiding data fields

To hide data fields you need to define private data fields. In python you can create private data field using two leading underscores. You can also define a private method using two leading underscores.

Let’s see an example

Expected Output:

Let’s try to access __balance  data field outside of class.

Expected Output:

As you can see now __balance  is not accessible outside the class.

In next chapter we will learn about operator overloading.

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4 Comments on "Python Object and Classes"

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K.B.
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K.B.
10 months 5 days ago

In the 2nd example, comment on line #18 (# method which returns a string) does not seem correct: the method returns self.__balance which is not a string. line not cleaned up after copy paste maybe?

Jody DeRidder
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Jody DeRidder
2 years 2 months ago

b1.deposit should be 900

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