Inheritance in Python | Python Tutorials for Beginners #lec89

Summary

This video introduces the concept of inheritance in Python, explaining its importance in object-oriented programming. The instructor discusses how inheritance allows a class (child class) to acquire attributes and methods from another class (parent class), similar to how humans inherit traits from their parents. The video highlights the efficiency inheritance brings, reducing redundant code and increasing maintainability. Key points include class syntax, method overriding, and accessing parent class methods using the `super()` function. The session concludes by emphasizing how inheritance promotes code reusability, clarity, and customization in Python programming.

Takeaways

• 🧬 Inheritance in Python is analogous to inheriting traits from parents in real life, where properties, appearances, and behaviors are passed down.
• 🏗️ In object-oriented programming, inheritance allows a class (child/derived) to inherit attributes and methods from another class (parent/base/super), promoting code reusability.
• 🔑 The base class is the class being inherited from, while the derived class is the new class that inherits properties and behaviors.
• 📝 The syntax for inheritance in Python involves using the `class` keyword, followed by the derived class name and the base class name in parentheses.
• 🛠️ Inheritance reduces redundancy by allowing methods and attributes from an existing class to be used in a new class without rewriting them.
• 🔄 Derived classes can have their own unique attributes and methods, in addition to those inherited from the base class.
• 🔧 Method overriding allows a derived class to provide a specific implementation of a method that is already defined in the base class.
• 🔄 The `super()` function is used in Python to access methods and attributes of the base class, including calling the base class's constructor.
• 🔑 If a derived class defines its own constructor, it must call the base class's constructor using `super().__init__()` to ensure proper initialization.
• 📈 Inheritance enhances code maintainability and readability by allowing for a clear hierarchy and structure in the codebase, making it easier to manage and understand.

Q & A

What is inheritance in Python?

Inheritance in Python is the ability of a class to inherit properties, methods, and attributes from another class. The class from which properties are inherited is called the base or parent class, while the class that inherits is called the derived or child class.

Why do we use inheritance in Python?

Inheritance is used to increase the reusability of code. Instead of writing duplicate code in different classes, a derived class can inherit methods and attributes from a base class, making the code more efficient, readable, and maintainable.

How does inheritance relate to real life?

In real life, inheritance refers to inheriting traits or properties from parents, like physical appearance or behavior. In programming, inheritance allows one class to inherit properties and behaviors (methods and attributes) from another class, similar to how a child inherits traits from parents.

What is the basic syntax for inheritance in Python?

The syntax for inheritance in Python involves defining a derived class and passing the base class as a parameter within parentheses. For example: `class DerivedClass(BaseClass):` followed by the class definition.

What are the benefits of using inheritance in large-scale projects?

In large-scale projects, inheritance helps save time by reducing redundancy, lowering the number of lines of code, improving readability, and enhancing maintainability. It also promotes code reuse, which is vital for managing large projects with multiple classes.

What is method overriding in Python?

Method overriding occurs when a derived class defines its own version of a method that is already defined in its base class. This allows the derived class to provide specific behavior for the method while keeping the same method name.

How can you call the base class method from a derived class in Python?

You can call the base class method from a derived class by using the `super()` function. This function gives access to the methods and attributes of the base class, allowing the derived class to extend or modify the behavior of the base class method.

What is the purpose of the 'super()' function in inheritance?

The `super()` function in Python is used to call methods or access attributes from the base class. It allows the derived class to inherit functionality from the base class without redefining it and can be used to extend or add new behavior to existing methods.

Can a derived class have its own attributes and methods in Python?

Yes, a derived class can have its own attributes and methods in addition to the ones it inherits from the base class. This allows the derived class to add specific functionality or properties while still using the inherited features.

What happens if a derived class defines an '__init__' method but also wants to use the base class's '__init__' method?

If a derived class defines its own `__init__` method but also wants to use the base class's `__init__`, it needs to call the base class's `__init__` method using `super().__init__()`. This ensures that the base class’s initialization is also performed.

Outlines

00:00

📘 Introduction to Python Inheritance

The speaker introduces the concept of inheritance in Python by relating it to real-life inheritance from parents, such as inheriting properties, physical traits, and behaviors. The speaker explains how this real-life concept translates into object-oriented programming, where classes inherit attributes and methods from other classes. The base class (or parent class) passes down its features to the derived class (or child class), and this forms the foundation of inheritance in Python.

05:02

❓ Why Use Inheritance?

This section focuses on why inheritance is important in programming. The speaker emphasizes the need to understand the purpose of inheritance before diving into its implementation. By using inheritance, code can be reused, which saves time and effort, especially in large projects. Inheritance reduces redundancy by allowing a derived class to inherit attributes and methods from a base class instead of rewriting them from scratch. This increases code readability and maintainability.

10:04

🛠 Practical Example of Inheritance Syntax

The speaker explains the syntax of inheritance with a practical example. A 'Human' class is created with methods like `eat` and `work`. A second class, 'Male', is shown to inherit these methods from the 'Human' class. The speaker highlights that instead of duplicating code in the derived class, we can reuse the methods from the base class through inheritance. This makes the code shorter and more efficient.

15:04

🎯 Inheritance in Action: Accessing Base Class Methods

In this paragraph, the speaker demonstrates how the 'Male' class can access methods from the 'Human' class using inheritance. The importance of reusability is stressed, as it reduces lines of code and increases efficiency. The speaker also explains that the derived class can have its own unique methods in addition to those inherited from the base class, showcasing flexibility in class design.

20:06

🔄 Overriding Methods in Derived Class

The speaker introduces the concept of method overriding, where the derived class can redefine a method that exists in the base class. In the example, the `work` method is overridden in the 'Male' class to represent a specific behavior (`I can code`), different from the general behavior defined in the 'Human' class (`I can work`). This demonstrates how derived classes can customize or specialize inherited methods.

25:06

🚀 Using the Super() Function for Enhanced Inheritance

Here, the speaker introduces the `super()` function, which allows a derived class to access methods and attributes of the base class while also adding additional functionality. An example is provided where the `work` method from the base class is extended in the derived class to include both the base class’s behavior and the new behavior. This approach is useful for enhancing inherited methods without completely overriding them.

Keywords

💡Inheritance

Inheritance is a key concept in object-oriented programming (OOP), allowing a class (child class) to inherit properties and methods from another class (parent class). In the video, the speaker uses a real-world analogy of inheriting features like appearance and behavior from parents to explain how a class can inherit attributes and methods from another. This concept saves time by reusing code rather than rewriting it.

💡Base Class

A base class, also known as a parent class or super class, is the class from which attributes and methods are inherited. In the video, the 'Human' class is used as a base class, with its methods and attributes like 'eat' and 'work' being inherited by a derived class 'Male'.

💡Derived Class

A derived class, also known as a child class or subclass, is the class that inherits attributes and methods from a base class. In the example from the video, the 'Male' class is the derived class, inheriting features from the 'Human' base class. This demonstrates how inheritance creates a hierarchy between classes.

💡Reusability

Reusability refers to the ability to use existing code again, particularly through inheritance. The video emphasizes that inheritance improves code reusability by allowing child classes to reuse the code of parent classes, avoiding redundancy and saving time. This also makes the code more maintainable.

💡Overriding

Overriding is when a derived class provides its own implementation of a method that is already defined in its base class. In the video, the 'Male' class overrides the 'work' method of the 'Human' class. Instead of 'I can work', the 'Male' class prints 'I can code', showing how a child class can customize inherited methods.

💡Super Function

The super function allows access to the methods and attributes of the base class from within the derived class. In the video, it is used to access the 'work' method from the 'Human' class while still allowing the 'Male' class to add extra functionality like printing 'I can code'. It plays a vital role in method overriding and extending inherited functionality.

💡Attributes

Attributes refer to the variables or properties that describe an object. In the video, the 'Human' class has attributes like 'num_eyes' and 'num_nose', which represent characteristics shared by humans. These attributes are inherited by the 'Male' class, showing how attributes can be passed down through inheritance.

💡Methods

Methods are functions defined within a class that describe the behaviors of an object. In the video, the 'Human' class has methods like 'eat' and 'work', which describe actions that all humans can perform. These methods are inherited by the 'Male' class, illustrating how methods are reused in inheritance.

💡Class

A class is a blueprint for creating objects in object-oriented programming. In the video, the speaker explains how classes, such as 'Human' and 'Male', are used to define attributes and methods. The class structure is central to understanding inheritance, as it allows the reuse of code across multiple classes.

💡Object

An object is an instance of a class, containing specific data and behaviors defined by the class. In the video, 'male_1' is an object of the 'Male' class, created to demonstrate how methods and attributes are accessed and used. Objects are essential in inheritance as they represent the real-world entities that are described by classes.

Highlights

Introduction to object-oriented programming (OOP) concepts in Python, focusing on classes and objects.

Introduction to inheritance: why it is needed and its benefits in OOP.

Inheritance in real life: explaining how children inherit properties and behaviors from their parents as an analogy for inheritance in programming.

Basic explanation of inheritance in Python: inheriting attributes and methods from an already existing class to a newly created class.

Clear distinction between base (parent) class and derived (child) class in inheritance.

Importance of reusability: inheritance reduces code repetition by reusing methods and attributes from parent classes.

Demonstrating the syntax of inheritance with an example: using the 'class' keyword, followed by the derived class name and the base class in parentheses.

Practical example: creating a 'Human' class with methods 'eat' and 'work', and inheriting them in a 'Male' class.

How inheritance reduces code redundancy: saving time and improving readability by avoiding repeated method definitions.

Overriding methods: derived classes can have their own specific implementation of methods inherited from the base class.

Using the 'super' function to call methods from the base class in addition to defining new behavior in the derived class.

Attributes in inheritance: derived classes can access attributes of the base class using the 'super' function.

Explaining the purpose of the 'init' method in classes and how it initializes object attributes in both base and derived classes.

Handling errors when missing required attributes in the constructor method and how to pass parameters using the 'super' function.

Summary of key advantages of inheritance: code reusability, readability, maintainability, and extending functionality with minimal effort.

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 or programming Concept

in Python so till now we have discussed

classes and object concept right now the

second thing is the second important

concept of Hope is inheritance so that

thing we'll see in this video what is

inheritance and the important

thing is why inheritance why you need

inheritance the need the benefits of

using this concept because whenever you

go to A New Concept you must first clear

this answer why you need that concept

why you are studying that concept the

need of that thing so the need of

inheritance why obviously there are some

benefits of using this concept that is

why we are using this conception but

what are those what are those benefits

this thing we'll see practically with

the help of programs right first we will

see basically what is inheritance right

now

don't go too into that programming kind

of thing in just real life we inherit

properties from our parents right means

if our parents are having some

Properties or some business means

automatically we are means that property

or business belong to

us right not just this we inherit like

now uh that appearance also like my eyes

are exactly same as my mother's eyes

so we inherited the appearance the

features like maybe your nose is same as

your father's nose

like this right maybe your height

whether you are tall or you are you know

sure it depends on your parents height

like this

right

so each other you can say it's in our

genes

not only the these properties not only

the appearance we also inherit the

behavior of our parents

like sometimes maybe you uh you have

faced this kind of situation you just

you know

you behave in a weird way and maybe your

mother say like father like son

means

or maybe your father or your parents are

having anger issues they are short

tempered and so you are your also are

having anger issues you are also short

temper

you also react same as your parents or

your father or your mother behave you

know in a particular situation you also

you know react or you also behave in

that situation exactly same means we are

inheriting the behavior also from our

parents or maybe from our grandparents

right this is I think you know and also

you have experienced this thing and

obviously you can uh like right now you

can feel this kind of thing maybe right

now you can feel this kind of thing

right

so this is what inheritance in real life

fine now this concept we can implement

in programming

right with the help of object only

programming there we have a concept of

inheritance right means we can say like

uh in programming we have classes till

now we have discussed classes and

objects

so classes are just blueprints those are

having some attributes and methods

attributes mean means what what an

object has are attributes what an object

does the methods those are methods

so in a class

we are having these attributes and

methods

right now inheritance is the ability

to inherit

the attributes or the method so you can

see the properties of the class or the

features of the class already created

class

to a newly created class

we can inherit all these attributes and

methods from this class

into another class

so this class is

this is basically

from here we are inheriting these

attributes and methods so this is known

as base class or parent class

or super class

and the second class which inherit

see which inherit these properties

attributes and methods from this class

this class is known as Drive class

or child class or subclass

right

so this is simple you can say

inheritance

so we can say inheritance is the ability

to inherit the features or the

properties or the attributes and methods

from an already existing classes or

already created classes into newer

classes that we make right rather than

creating that class from scratch we can

inherit these features

okay

now this is what inheritance but why why

we are inheriting these attribute and

methods we can also write down our

attributes and methods in this class so

why inheritance the answer of this

question is important so if you got the

answer of this question why inheritance

and you understand this thing

then means you are done almost you got

everything about inheritance yeah we are

studying many things like types of

inheritance and many other things but

the answer of this question is important

one before proceeding further why why

inheritance so this thing now I'll see

you with the help of program right okay

let me just first tell you the syntax

before

you just write down a name this keyword

class then

this derived class name

right and in bracket we write down

Base Class name

and the colon and here the class

definition

whatever you want to Define in this

class that definition you can write

right

so now here you're gonna like like class

definition or statements

so this is simple syntax of inheritance

now let's see practically

okay so let's create a new file here

inheritance intro dot py right

I am simply

Define the class and the class name I'm

taking like human

okay now I'm defining some functions

like eat

and in it simply I am printing like I

can

eat

and one more function suppose I am

defining like work

right

and simply I am going to print here I

can work

so these two methods sorry not function

these are two methods eat and

not word its work I can work

right now

let's define see I'm having only right

now methods no attributes that was we'll

see later about attributes now I am

having a class

and suppose I am having a class mail

right

now obviously Paul male and obviously

females are human human being

so male can also eat we know male can

also work right

now one way is either in mail also you

can Define these two functions for male

and like this Ctrl C and

they eat deaf work I can work I can eat

right and simply if I like if I create

an object of male male underscore one

any name you can take and I'm creating

an object of this male class

right and with the help of this now male

object male dot see eat and work these

two methods are from this male and male

class as you can see right so you can

access these methods like if I access it

and if you run this then obviously it

will print

I can eat see right but the thing is

this is what just a waste of time

right and just to increase the number of

lines in our code unnecessarily because

we are just repeating these lines these

two things

if you are a human obviously male or

human so they can eat and they can work

so rather than writing again

I can just use these

methods these are these are already

defined these are already in this

already created class so rather than

creating this class from scratch what I

can do

I can just inherit these methods so this

is what inheritance and this will

definitely save a lot of time because

here we are I'm only two classes and

only two methods small example but on

industry level there are multiple

classes and very large project on very

last project we are working right so

obviously this is going to save a lot of

time and less number of lines in our

code so that is why if less number of

lines then readability of our code will

automatically increase maintainability

as well as readability right so these

are I guess you are getting now the

benefits of using this concept so this

is same the answer of why we need

inheritance so now so the syntax I have

told you derived class name and in

bracket you just have to pass simply the

base class

from this class I am going to inherit

these two features so these two methods

so just write down the name of that

class that's it now if you don't want to

Define anything in main class obviously

male class if we cannot leave this like

this so just have to pass

just a past statement means we we don't

know what to write down in this mail

class right now but later on we will

Define this class also right now in mail

now see with the help of this male

object

mail one

can you access eat and walk see

here also see the difference now method

eat and what you can access but here see

the name of the class is human human and

at previous case the name of the here

the class was male and male so from

Human class we are accessing it and self

so this is inheritance so now also I can

print I can access it and yeah I can eat

so the main purpose of inheritance is to

increase the reusability of the code we

are either using this code again rather

than writing this again we are just

using it

right

now

this thing this is the simplest concept

of inheritance the second thing is this

derived class

can Implement can have its own

attributes and its own behavior

right like we

we can have our own behavior it's not

like that everything the all the

properties all the appearance properties

and all the like our Behavior we inherit

from our parents know

we are having our own identity maybe

their their you know uh

uh their way of doing some work is

different our way of doing our work is

different so we can have different

Behavior so like this the derived class

can also have its own attribute and

methods so right now just I'm not taking

the attributes I'm taking just methods

so I'm just defining a method one more

method like maybe flood

no offense

it's just an example don't take it

seriously

so I can

see

these now see using this mail how many

thing you can access male dot

eat and work from Human class and flirt

from male class all the three methods I

can access right so if I access this

slot so it will print yeah I can flirt

right and both if I want to access like

male 1 Dot and work

this is also fine see I can plot I can

work

right so this work

this may class is accessing from human

and this is its own method so our own

attribute and methods we can Define this

is second thing

third Point important is

this derived class can have its own

implementation

of the method that has that are already

defined in human class

now what does that mean let's see

practically if you're not getting my

words see

I am

taking the same method work

from Human class work right but my way

of work is different from Human class so

I can redefine this method here

so my way of work is

like maybe I'm specific I can call

so I have just I am my I'm having my own

implementation of this work method and

this women class is having

implementation of this work method I can

work but I am having I can code

so this particular thing is called

overridden this is what

override concept method over it

overriding

means you have overruled this method

work method previously this but you have

overrun this method right now if you

want to access using this object mail

one dot C flirt walk from male eat from

Human

see this work is from male you are

accessing not from Human because I am

having my own implementation

of this method so if you print

work then it will print not I can walk

it will print I can code because you

have overridden this method I can plot I

can code

right

this is overriding concept

okay fine now next point is

if you want if you want to have this

this definition also this Implement

implementation also as well as you want

to add something extra

in that definition of that method

see means I want to print I can work as

well as I can code

right I am not

ah implementing I am not defining this

method from the scratch I want the

previous definition from the base class

and I want to add some extra

right

so that what how you can do that you can

access with the help of we have a

function

super

just call this function dot what method

see with the help of super it indicates

that

from Human class from Super means

superclass we know the base class so

Base Class is what class you have passed

here human so this is human is what the

base class so from Base Class you can

access all the attributes and methods of

that class

right with the help of with the super

Super Dome now work see human and eat so

work

sorry

and I want to access this thing super

dot work right

now see let's print mail one dot work

see I can plot and I can work I can code

now this work definition is

because we have accessed this

implementation from Super so it will

print I can work as well as now I have

added my extra feature means one more

statement I can code so both think it

will print and now if you see here

this work is from mail only not from

human male only

right

so I hope you got this thing right I can

figure out I can work I can code

so these kind of thing you can do now

this is about methods if suppose I am

having attribute 2.

so so this super class the super

function is basically give you the

access to all the methods and attributes

of parent class right so let's define

some attribute also I am having a init

function and there

I'm having like two attribute all the

human are having like maybe two eyes

maybe not not maybe yeah definitely they

are having two eyes so numb underscore

ions equal to I'm setting two right and

nose

number of no is equal to one only two

attribute I am taking number five is the

number of nodes so obviously male is

also having the same thing number of

eyes and knows two eyes and one knows

right

now see

with the help of

this male object

now you can access and number of nose

from Human class and number of eyes from

Human class right so if you want to

print Nam underscore ions

I want to print this thing so let's

print

how many number of eyes uh this male

object are having

so let's run this and it will show you

see I can flirt I can work I can code

random number of eyes are two

number five is two

we haven't defined any attribute in mail

but it is accessing from parent class

like this

and if

rather than eyes and nose I want to

specify one more attribute specifically

for mail so that also you can do with

the help of depth I want to

initialize and like

I want to pass one parameter name name

of the mail

with this class right so while calling

this now creating object you have to

pass name

so I'm writing like self thought name is

equal to

name

right now it will give error while

calling this object because see

in line number 17 while you are creating

this object mail type error mail in it

missing one required positional argument

name because in defining in this

Constructor you have to pass

this parameter name so let's pass this

name

maybe Akash

let's send this

mail object has no attribute Namaz

see

no attribute

num eyes

why so because see last time

in line number 20 because you are

printing numbers and mail object is not

having attribute namise in mail object

now I am having only name attribute

but see now at this point of time

let's see let me just show you this

thing

if you want to print mail One Note

then name

Namaz are from human number of nose from

human and maybe you think you can access

let's access number of nose

maybe you think it should print let's

comment out this these lines work and

all

I'll just print number of nodes

see it is not printing anything male

object has no attribute num nose why you

are getting this attribute because this

is dried glass we can access all the

attribute from here

because now you have defined your own

init function here

right

now if you want to access these

attributes

if you want to access these attributes

then you have to use super function

function so yeah we can use these

attributes as well but for that in this

init function in this derived class init

function you have to call

this super function

Dot

in it

init function of super

right

and now that's fine

now let me just run this see if again

mail one don't

name number of nodes number of eyes from

human and work plot and these are the

methods eat as well as from human right

so number of nose or number of eyes I

want to print

let's run this and it will print number

of eyes are two

okay

if I'll print the name

mail one dot

name so it will print

C Akash

right so this is what the beauty of this

super function it will give you the

access

of all the attributes and methods of

superclass

right

because here you have if you don't

Define your own init function it's okay

without any super function you can use

this thing but if you if you have

defined

your own init function in that case you

have to call Super function to access

the attribute of

parent class

see the difference here right in case

here also I want to pass one argument

like maybe

self Dot

heart equal to

foreign

because this time this initialization is

also having one parameter

if you run this like this

see

in line number 19 because you are

calling this Akash and in line number 12

super init this type error women don't

init missing one required positional

argument num heart

in line number 12 in line number

12.

so you have to pass one argument num

hard any other name you can take it's

not like that you have to use this

number same name so I am calling suppose

heart only heart

right

okay

still it will give an error see now

maybe you think we have passed one

parameter name as well now why it is

giving an error let's run this here

heart is not defined as well as see this

line line number 19

Akash

here also we got an error see you are

you are accessing all the attributes

from this human class right means one

parameter is nam hard so rather than

name one more you have to pass here

one more attribute for number of heart

to the seed number of R so hard right

and whatever you write down the

parameter name you have to pass the same

parameter name in super init

it's not compulsive that these should be

same as this parameter this can be

different right now it will work fine

now it will give error because Akash as

well as okay let's run this whatever you

will get see

while calling this mail one while

creating this object this is missing one

required positional argument r so

obviously you have to pass your name as

well as R so Akash comma one heart

and if you print here

using male 1 Dot

see you can access now

this attribute of human class

foreign or if suppose I want to define a

function here

one more function like display and

simply I want to print here

using F string

like High

m

name of this object

on which you are calling so I am

the name obviously we can

Fetch with the help of we have a name

attribute here name so I am self dot

name

and suppose I want profit I have

number of Parts how many number of part

so this much

hard

from where you can fetch the value of

this heart

from

self dot C

um hard from Human

and other than this just call this

display

mail one dot

display let's run this

hi I'm Akash and I have one heart

although the smell is not having any

attribute numb heart but still we are

using self-load numb heart because we

are accessing this from the parent class

the same attribute num underscore heart

not simply hard or hard just a parameter

name

the attribute name is nam underscore

Heart Like This

so now you got the main purpose or need

or use or you can say advantage of

inheritance concept

what main purpose of inheritance is

reusability of the code because we can

create

a new class from already existing class

right we can inherit all the features

and attributes the methods from already

created class rather than creating our

class derived class from scratch right

and that will definitely save a lot of

time

right so it enhanced the reusability of

the code and your code would be more

maintainable more readable

right and as well as a child class can

provide its own specific implementation

of the methods that

inherit that the class derived class

inherit from base class right or you can

add in child class also you can add your

own attribute and methods right

so now I hope you have a basic idea of

inheritance and why we need inheritance

some use of inheritance or you can say

advantage of using this concept right

now in the lecture we will see types of

inheritance so now it's in the next

video till then bye bye take care