Self and __init__() method in Python | Python Tutorials for Beginners #lec86

Summary

In this video, the speaker continues their Python Object-Oriented Programming series by discussing how to add attributes and initialize objects in a class using the `__init__` method. They explain the role of constructors, the `self` keyword, and how to set default values for attributes like Instagram followers. The video emphasizes simplifying object creation by reducing code lines and concludes with an assignment for viewers to practice creating new objects with attributes. The next video will cover adding methods to the class.

Takeaways

• 📚 The video continues a Python programming series focusing on object-oriented programming.
• 🧑‍🏫 The instructor discusses creating classes and objects, building on concepts from the previous video.
• 🏗️ The key topic in this video is adding attributes to a class and introducing the `__init__` method, which serves as a constructor.
• 🔑 The `self` keyword is explained as a way to reference the current object when creating attributes or methods within a class.
• 💡 The purpose of the `__init__` method is to initialize the attributes of an object automatically when the object is created.
• 🔄 Each time an object is created, the `__init__` method is called to set up the initial state of that object with the given parameters.
• 📝 Examples are provided on how to add attributes like `name`, `address`, and `followers` to a class and initialize them using the constructor.
• ❗ The instructor emphasizes that attributes must be accessed using `object.attribute` syntax and demonstrates how this works.
• 🚀 Default values for attributes (like setting default Instagram followers to 0) can be added, reducing the need for repetitive code.
• 📌 An assignment is given at the end, asking viewers to create more instructors with name and address attributes, and print their information.

Q & A

What is the purpose of the `__init__` method in Python classes?

The `__init__` method in Python is a special function that acts as a constructor. Its primary purpose is to initialize the attributes of a class when an object is created.

Why is the `self` keyword used in class methods?

The `self` keyword is used to refer to the current instance of the class. It allows the method to access and modify the object's attributes and ensures the method operates on the correct object.

How do you assign attributes to an object of a class?

Attributes can be assigned directly to an object using dot notation, like `object.attribute = value`. Alternatively, attributes can be initialized inside the `__init__` method by assigning values to `self.attribute`.

What happens if you don't pass any parameters to the `__init__` method?

If no parameters are passed to the `__init__` method, and it expects them, Python will raise a `TypeError`, stating that required positional arguments are missing.

What is the advantage of setting default values for parameters in the `__init__` method?

Setting default values for parameters allows you to create objects without providing values for those parameters. This is useful when certain attributes are optional or have a standard default value.

Can you modify the attributes of an object after it has been created?

Yes, attributes of an object can be modified after its creation using dot notation, such as `object.attribute = new_value`.

What is the difference between a class attribute and an instance attribute?

An instance attribute is specific to each object of a class and is set using `self.attribute`, while a class attribute is shared across all instances of the class.

What does the error 'missing required positional argument' indicate?

This error occurs when a function or method, like `__init__`, is called without providing the necessary arguments it expects, leading to an incomplete call.

Why is using a class beneficial for managing multiple similar objects?

Using a class allows for better organization and reusability of code, as it provides a blueprint for creating multiple objects with similar attributes and methods, reducing repetition and potential errors.

How would you create a new object with attributes in a Python class?

To create a new object with attributes, define the class with an `__init__` method that initializes the attributes. Then, create an object by calling the class and passing the necessary parameters to the `__init__` method.

Outlines

00:00

📚 Introduction to Object-Oriented Programming in Python

The speaker introduces the topic of Object-Oriented Programming (OOP) in Python, building on concepts discussed in previous videos such as classes and objects. They mention that the current video will focus on adding attributes and methods to classes, particularly the `__init__` method (Constructor) and the `self` keyword. The speaker also highlights the importance of constructors for initializing object attributes, which will be demonstrated in this video.

05:02

💻 Overview of a Python Programming Competition

The speaker briefly shifts focus to announce a Python programming competition called Ultra Combat, hosted by Anacademy. It offers up to 90% scholarships and various rewards such as MacBooks and smartphones. The competition, geared toward GATE and ESE aspirants, consists of 40 MCQs to be answered within 120 minutes. Participants can register for free using a provided code, and the event is scheduled for July 23 at 11 AM. The speaker encourages viewers to check the description box for further details and relevant links.

10:02

🧑‍🏫 Explaining Class Attributes in Python

Returning to the Python topic, the speaker explains how to add attributes to a class, using an example of an 'Instructor' class with attributes like `name` and `address`. The speaker demonstrates that attributes are specific to objects, and to access these, you must reference the object (e.g., `instructor1.name`). They show how assigning attributes directly to an object can lead to inconsistent and inefficient code, especially when handling multiple instructors. This highlights the need for a constructor (`__init__` method) to automate the process of initializing object attributes.

15:02

🔧 Introducing Constructors and the `__init__` Method

The speaker introduces the concept of constructors in Python using the `__init__` method, which automates the initialization of object attributes when an object is created. They clarify how `self` binds attributes to the current object and demonstrate the syntax of defining attributes such as `name` and `address` within the constructor. By automating attribute initialization, constructors help streamline object creation and reduce code repetition, making it easier to manage large numbers of objects.

📝 Example of Using Constructors to Simplify Code

The speaker walks through an example where the `__init__` method is used to create two instructor objects, passing attributes like `name` and `address` directly at object creation. They highlight how omitting required parameters results in errors and explain the role of `self` in binding values to the correct object. The example demonstrates how constructors simplify the code by eliminating the need to manually assign each attribute to every object.

🛠️ Using Default Values for Attributes in Python

The speaker explains how default values can be set for optional attributes like `Instagram followers`, which not all instructors may have. By setting a default value (e.g., `followers = 0`), the speaker shows how Python allows flexibility in creating objects without specifying every single attribute. This feature saves time and code, as default values can be overridden when necessary, but they prevent repetitive zero assignments for attributes not applicable to all objects.

💡 Assignment and Upcoming Lesson on Adding Methods

As the video wraps up, the speaker assigns viewers the task of creating two more instructor objects and printing their `name` and `address` attributes. The speaker teases the next video, which will cover adding methods to classes, building on the concept of attributes by focusing on what the objects can do, not just what they are. The video concludes with a thank-you message and an invitation to continue learning in the next installment.

Keywords

💡Object-Oriented Programming (OOP)

Object-Oriented Programming (OOP) is a programming paradigm where code is organized into 'objects' that contain both data and functions. In the video, the instructor explains how Python uses OOP concepts like classes, objects, and methods to structure programs in a more organized and reusable way.

💡Class

A class is a blueprint for creating objects in OOP. It defines a set of attributes and methods that the objects created from the class will have. In the video, the instructor discusses how to create a class and explains that it’s a user-defined data type, which allows developers to structure their code around real-world entities.

💡Object

An object is an instance of a class, meaning it is created from the class blueprint and can have its own unique data. The video demonstrates how objects are created from classes and how they hold attributes like name and address. Each object is a separate entity with its own values for these attributes.

💡Attributes

Attributes are variables that belong to an object or a class. They define the properties or characteristics of an object. In the video, the instructor shows how to add attributes like 'name' and 'address' to an object and discusses how these attributes are tied to specific objects, helping to store important information.

💡__init__ Method (Constructor)

The __init__ method is a special method in Python classes used to initialize the attributes of an object when it is created. The video explains that this method allows developers to assign values like 'name' and 'address' to an object automatically when the object is instantiated, streamlining the object creation process.

💡Self Keyword

The self keyword in Python is used within a class to refer to the current instance of the object. It allows methods and attributes to be accessed and modified for the specific object being referenced. In the video, the instructor explains that 'self' helps bind the attributes and methods to the object being created or modified.

💡Methods

Methods are functions that are defined inside a class and describe the behaviors or actions of an object. The video focuses on how methods will be discussed in a later lecture, differentiating them from attributes, which describe the object’s properties.

💡Default Values

Default values in function arguments allow a parameter to take on a predefined value if no argument is provided during function or method calls. The video demonstrates this with the example of 'Instagram followers', where a default value of 0 is set, reducing the need for manually passing '0' every time an instructor doesn’t have followers.

💡Gate and ESE Combat

Gate and ESE Combat is a competitive scholarship exam mentioned in the video, offering up to 90% scholarships and rewards like laptops and mobile phones. The exam is designed for students preparing for engineering entrance exams like GATE, covering subjects such as General Aptitude and Technical topics.

💡User-defined Data Type

A user-defined data type is a data type that is defined by the user in a program, rather than a pre-existing data type in the language. In the video, the instructor describes how a class functions as a user-defined data type, providing a structure for creating objects with specific attributes and behaviors.

Highlights

Introduction to object-oriented programming in Python and recap of previous concepts like classes and objects.

Discussion on adding attributes and methods to a class, focusing on how to initialize objects.

Explanation of the `__init__` method and its importance in initializing object attributes when creating an object.

Introduction of the `self` keyword and its role in referencing the actual object that is calling the method.

Demonstration of how to create object-specific attributes using `self` and initializing them within the `__init__` method.

The concept of a constructor in Python is explained as the `__init__` method that runs automatically upon object creation.

Explanation of how to pass arguments like name and address while creating an object to initialize its attributes.

Detailed walkthrough of assigning attributes to individual objects and how it reduces redundancy in the code.

Illustration of the problem of assigning attributes manually for multiple objects and how the constructor solves it.

The `__init__` method is demonstrated by passing custom attributes such as name and address to multiple instructor objects.

Example of handling default values for attributes, such as Instagram followers, where not all objects require a specific value.

Using default values in constructors to simplify object creation when some attributes are optional or have common values.

Demonstration of printing object-specific attributes like name and address for multiple instructor objects.

Assignment to create additional instructors and practice initializing and printing their attributes, reinforcing the concepts.

Teaser for the next video, which will cover adding methods to classes, further enhancing the functionality of object-oriented programming.

Transcripts

hey everyone I hope you all are safe and

doing good so in the series of learning

Python programming language we are

discussing object-oriented programming

in python in the previous video we have

seen like what is in class what is an

object how to create a class how to

create an object why do we need classes

this thing we have discussed right

but we haven't like we have created our

own class but we haven't added any

attributes or methods in that class so

that thing we'll be discussing in this

video

how to add attributes what is that init

method underscore underscore N8

underscore underscore and in bracket a

self keyword is passed as a parameter

right so what is that method what is

basically the fund of Constructor

right how to initialize objects while

creating those objects of a class so

these things will be discussing in this

video right but before that this one

will tell you something it is especially

important for gate and ASE as parents an

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conducted on 23rd of July and the timing

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and what how many question you will get

the pattern is 40 mcqs you will get and

the time limit would be 120 Minutes

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you can use my code jkl10 to enroll for

free in this combat right so all the

relevant links and information you will

find in the description box of this

video you can go and check out okay now

let's see this was the class we have

created in the previous lecture the

class instructor and we have done

nothing here no attribute nothing else

just pass and we have created one object

and if you find out the type of this

object then it will give you instructor

right just forget about this and

response for main underscore that also

will I'll tell you in later videos so

the classes this instructor so class

means basically it's a user defined data

type

that it has a blueprint to create object

okay now how to add attributes see if in

instructor obviously the instructor is

having some name or ID or information

the main information so one way is

instructor one

instructor one

dot name I am assigning like maybe

pile

right you cannot simply write down here

just name is equal to Pi

that would be simple a variable but now

this name is an attribute of this

instructor

this instructor is an object that is why

we are writing instructor dot name this

name is now attached with this

instructor with this object right so

that is why this is now attribute one

more thing if you want to check like

instructor

Dot

address is equal to

Delhi

right and if you want to fetch if you

want to print this information then how

you can press simply we cannot write

down like print name

let's run this and what see what you

will get

name is not defined

because name is

its name is what instructor one dot name

it's not just simply name a variable no

it's now an attribute of this object so

you must write here instructor 1 dot

name this is the syntax right if you

assign value to an object like this and

if you want to fetch the value so

instructor one dot name this time it

will give pi

right

like this if like I have a YouTube

channel I want to hire now 10 instructor

to teach different different subjects

and like the attribute of this

instructor these instructor would be

many attribute I want to store like name

address and like maybe ID and phone

number has camera has laptop has books

these are simple attributes

so for one instructor I want to store

every information so same you can

instructor one note name this instructor

OneNote address instructor one dot ID

instructor one dot phone number

instructor one dot has camera and like

this you can write down these lines

and like this if I want to create one

more instructor

so in that case what will happen

instructor 2 is equal to this same

method now instructor two dot name and

instructor two dot address and if I want

to print instructor two dot name that is

also fine it will print pile and

okay there is some error here

like this so it will give let's just

rename this otherwise it will give same

name so like Jenny

so it will give pile and jelly

like two name like this if you want to

store information of 10 instructor then

definitely it

is not easy because we are it's so

hectic so many number of lines

right and maybe like name here I'm

writing name here I'm writing username

over here I'm writing address or simply

instructor address maybe I can write

here instructor address

so the name of these attributes

would be maybe different

for each object for each object for each

instructor right so it would be not easy

to manage the information like this

right and definitely now what is the use

of class if we are writing this kind of

thing that we can do with the help of

simple variables we can create different

variables for each instructor of each

thing right

now for this

okay now class comes into picture

now here

we have for this thing we use the you

can say the concept of Constructor if

you are from C plus background if then

you must have heard about Constructor

right if not it's okay I'll tell you

here

so basically the task of an Constructor

is to initialize

the data members to assign values to the

data members of a class

when

an object is created

so Constructor will basically allow us

to specify what would happen when we

create this object when we create an

object what would happen

with the help of Constructor we can do

this thing we can initialize

the attributes the members of the class

while creating we don't have to write

down like instructor one dot name one

dot address and we have to initialize

separately no

right so here we have a special function

that is Def

and

this

init function so see it is not just a

simple function

because it is special one because it is

having underscore underscore init

underscore underscore then in bracket

also we have like cell it's

automatically I haven't written C cell

for like this

if you write down this thing simply i n

i then see you will got this thing self

it's predefined predefined right so it's

a special method

and python interpreter no it is a

special method and what it will do

python intermittent python interpreter

no knows about this method very well

right

now self is a key word why we are

passing this self that also I'll tell

you so in C plus plus we are having

Constructor to initialize object in

Python we are having this method init

method to initialize the object

to initialize the data members of a

class while creating an object

right

so same as Constructor it is doing the

same task

okay now see

and one more thing this init function

would be called every time you create

an object

right so see if you want to check out

this thing you can write down something

like this print

creating a new object I'm not writing

anything I'm just printing here creating

a new object and let's run this

see first creating a new object because

here

we are

creating an object so creating a new

object then pile it will print file

right then again creating a new object

and Jenny it will print so two time

this this would be printed so two time

you have called this init function right

this function has been called so this

one object we have created another

object we have created so every time you

create an object of a class this init

function would be called every time

right and it is used to like initialize

the attributes of that particular object

right

so the self is indicating it is

referring the actual object on which

right now we are calling this function

on which this function has been called

right now so if this function has been

called right now on this object

instructor 1 so the self is instructor

one

if next time this init function has been

called during this line instructor 2 is

equal to instructor so now at this point

of time the selfish instructor 2 so it

is referring to the actual object

right so when we are calling this then

it will initialize the instructor 1

object attribute this time at this point

of time it will initialize instructor to

object attribute so I hope now you got

why we are using this self keyboard here

right if you are still not getting it's

okay we'll do some practice here so I

want to like

pass name and address so like two

parameter we can pass name

and

address any name you can take right

and let's just remove the slime

right

now how to initialize the attribute of

the instructor only two attribute I am

taking name and address that's it so you

have to write down the self keyword cell

Dot

the name of the attribute what you want

the name of that review so I want name

is equal to

this is not compulsory that this name

this parameter name and this should be

same it may be different right so the

self name is equal to whatever argument

you will pass and that we will fetch

here in this parameter name name so you

have to write down here this name

right see the color this name and this

name is having same color but this name

is having different color so here the

attribute name you can take any things I

can take here like

instructor underscore name that is also

fine

Constructor and Square address but I am

taking here name that's it

so

self dot second attribute name I am

taking just address is equal to

this address

let's just take here

let's

rename this instructor underscore name

the parameter name so here you need to

pass

instructor underscore name now you got

the difference

this parameter name and this name should

be same and this attribute name you can

take

any name right it should not be

same with this parameter name right

okay now you don't need to assign the

value initialize the object attribute

like this what we can do just remove

these two lines and

while creating the object obviously this

init function would be called so now it

is expecting to pass these two parameter

name and address so here only I can pass

like Jenny and in address I am passing

like

Maybe gurgaon

right

and let's just comment out these lines

for instructor 2 and let's just print

instructor one dot name let's run this

and it will print the name

right so obviously it will reduce the

number of lines of code right

now for instructor to same

so instructor 2 and instructor see now

if I don't pass anything here and let's

run this

so you are getting an error

see

in line number 10 in line number 10 in

this line in this line

while you are creating this object then

this init missing two required

positional argument instructor name and

address right

so obviously this function would be

called init method would be called while

you are creating the object and you need

to pass these two parameter not three

maybe you think self is also there but

self is just a keyword to bind the

actual object

with the values right so by default self

at this time would be instructor 2 and

by default self at this time would be

instructor one so you don't need to pass

the value for self it is just a keyword

right so self is like basically just a

keyword to bind

it will bind the

objects attributes to the argument

received right

obviously now you need to pass two

argument here so I am passing like pile

and address is like

Delhi now this is fine you will not get

any error now you can face this

information right like this if you want

to create 10 instructor then definitely

now it would be easy and less number of

less lines of code

right

so this is the use of the class and this

init method I think it is clear to you

guys what is this in it what is the self

and all right now

if you want to pass like by default

let's take one example uh I want to pass

the Instagram follower of each

instructor maybe the instructor doesn't

are not on Instagram right most of the

teachers are not on Instagram so they

are having zero zero zero followers

right so that information is not

mandatory right obviously everyone is

having name everyone is having some

specific address so that for sure but

it's not compulsive that everyone is on

Instagram and having some follower

account right so if I pass here this is

the case if I pass here like

Instagram underscore

if I pass a parameter Instagram

underscore follower so maybe Jenny is

not like on Instagram so you need to

pass here zero and for pile also maybe

you need to pass zero so maybe 10

instructor for every instructor the

count is zero so why you are passing

zero zero it's just a waste of you can

save time

and they're not no logic to pass zero

zero zero so what we can what we can do

rather than

making this

in compulsory argument to pass we can

set default value of this parameter cell

Dot

followers is equal to 0.

and now see it's not like that if I am

on Instagram and I have some followers

so right now every object will be having

zero follower of this class all the

objects right but we can modify this

this attribute specifically for any

object like for Jenny if I want to

modify then I can modify that is also

fine that also will see

right but for now you have to be clear

this thing like you can pass default

value also for any attribute now for

every if I want to print like print and

instructor one dot

followers

now it will print a zero

see Jenny and zero because by default

the follower count for each object of

this class would be zero because we have

set a default value right

now I hope you got the idea like how to

add attributes how to initialize the

attributes of an object what is the you

know use of this init function what is

this self keyword like this

so now one assignment for you is okay

this is the class and all now you have

to create two more instructor right

passing the name and address and you

have to print the information name as

well as address for each instructor for

the two instructor right

so now that's it for this video in the

next video we'll see how to add methods

these are just attributes we haven't

added still methods what the instructor

will do we have just added what he or

she has not what he or she does right so

that thing we'll see in the next video

so thanks for the next video then bye

thank you