PYTHON INTERMEDIATE’S GUIDE | OBJECT-ORIENTED PROGRAMMING

 WHAT IS OBJECT-ORIENTED PROGRAMMING/OOP?

Object oriented programming, as the name suggests, is programming using different kinds of objects. We create an object using something called a class. A class is like a blueprint for creating objects. In Python, every object is an instance of a class, which means the object’s data type is the class that created it. For example, the data type ‘String’ is actually a class named ‘String’ in Python and so are all the other data types. Think of class as parents and objects are its children.

A class name should always start with an uppercase letter. We should always use camel case in class name, which means if a class consists of multiple words, the first letter of every word should be uppercase. This is usually done because spaces are not allowed in class names. For example, ‘ThisIsCamelCase’

Let’s take a look at a piece of code to understand OOP better:

class Orange:

            def __init__(self):

                        print(‘Created’)

apple=Orange()

So the explanation can seem a bit complicated at first but I am sure you brilliant people will get it in just a minute. So let’s give it a try. By the way, if you have no idea what I just did here, or don’t know what a method/function is, you should check out my article on modules here, it will not take much of your time, probably ten minutes and then you can come back right here.

Here, ‘Orange’ is the class name, and inside the class we defined a method called ‘__init__’ and passed in the parameter ‘self’. Now if you type this code in text editors like Sublime Text, you will notice that the colour of the method is different from other methods and parameter ‘self’ has its own colour as if it is a valid parameter by itself. This is because this is not an ordinary method, it is a magic method (I know LOL). All of this will be clear in just a moment. We defined a method which will print ‘Created’ when called. ‘apple’ is the object that calls the method ‘Orange()’ (again this would be clear if you check out my article on functions). If you are familiar with calling methods, you know we are supposed to pass in parameter if we initialized the method with a parameter and we did initialize it with ‘self’ but surprisingly we didn’t pass in anything when calling it. All of these will be crystal clear to you in the very next heading.

WHAT IS A MAGIC FUNCTION?

In Python, when you name a method ‘init’ preceded and followed by two underscores, you are defining a special method that Python calls every time you create a new object using that class. For example, in the above example, when you create an object using the class ‘Orange’, Python automatically calls and executes the ‘__init__’ method as well. It’s like you don’t have an option.

Any method surrounded by double underscores is called a magic method. A method Python uses for special purposes like creating an object.

When you define a method, it must always accept at least one parameter (except in special cases). The convention in Python is to name this parameter ‘self’. (Do you see all the dots connecting now?)

When you define a method with ‘self’ as a parameter, Python passes the object that method was called on back to it as a parameter. For example, when you called the class ‘Orange’, an object was created which was stored in the variable ‘apple’. Since we used ‘self’ as  a parameter while defining the method ‘__init__’, Python now passes that object as the parameter to the ‘__init__’ method. (I hope you see now why the parameter is called ‘self’)

When you create a new object, you don’t have to pass any parameter for ‘self’ as Python automatically does it for you. (Just like we did in our ‘apples and oranges’ example)

CREATING INSTANCE VARIABLES:

You can create instance variables using self. Instance Variables are basically variables that are exclusive to an object. If you want to use these variables, you must first create a specific object and then use that object to access these variables. So how do we create them using ‘self’? Let us find out:

class Fruit:

            def __init__(self,w,c):

                        self.weight = w

                        self.colour = c

This is the code to create an instance variable. As always, let us break it down.

When the class ‘Orange’ is called, it will create an object (as usual), but this time it will assign two instance variables (weight and colour) to it. So whenever we call the class ‘Orange’ we must now assign values to the variables ‘weight’ and ‘colour’ respectively. For example,

orange = Fruit(2, ‘Light Orange’)

So now the object ‘orange’ has the values ‘2’ and ‘Light Orange’ assigned to it as weight and colour respectively.

Now, you can call these variables anytime, using ‘orange.weight’ which will print ‘2’ or ‘orange.colour’ which will print ‘Light Orange’.

Note: An instance variable should always be defined inside the method ‘__init__’ except in special cases. And just in case if you are wondering, the method ‘__init__’ is not some random name of a method I came up with. It is a specific method. You can check this by typing in ‘def __init__’ and ‘def __random’ in Sublime Text 3 and notice the difference in the highlighting colours.

You can also change the values of instance variables just like any other variables. For example,

orange.colour = ‘Dark Orange’

Now the value of ‘orange.colour’ is changed from ‘Light Orange’ to ‘Dark Orange’.

CONGRATULATIONS !!! You now know what OOP is?, how to create instance variables? and what is a special method? Like I always say, Have fun with it !!! Create some cool programs. Good luck !!!!   

Let me know, if you loved it, hated it, want to kill me or any other sort of feedback in the comments section below. Also, if you have any queries regarding the topics taught in this lesson or previous lessons, you can always find me in the comments section or in the telegram channel where you can personally talk to me and ask me any question about anything we have learnt so far.

One more thing !! By the time you have finished reading this article, there is a surprise post waiting for you, check it out and I hope you enjoy it. I'll be waiting for you in the surprise post, see you there.

So, this was an introduction to Object_Oriented Programming Python. Stay tuned for another article next week, same time, where we will learn about The Four Pillars Of Object Oriented Programming. So more cool stuff coming your way, DON’T MISS IT !!

I hope this article answered all of your questions and even helped you in becoming a better programmer. IF IT DID, leave a like AND FOLLOW THIS BLOG TO BECOME A PROFESSIONAL PYTHON PROGRAMMER FROM A TOTAL BEGINNER. IF IT DIDN'T, feel free to ask any further queries in the comment section below.

If you are a beginner, intermediate, advanced or just someone interested in programming, feel free to join our telegram channel and be among people like you:

https://t.me/joinchat/AAAAAFVduJs3bF00nwKGUA

And do you know the best part? Joining it is FREE !!!

So go ahead click on the link and I will see you there. 

 HOPE YOU HAVE AN AWESOME DAY AHEAD !!!