Functions in Python | Introduction | Python for beginners #lec56

Summary

This video script introduces the concept of functions in Python programming. It explains the necessity and benefits of using functions through real-life analogies, such as sharing a recipe or a mother's multitasking. The script outlines how to define and call functions, emphasizing code reusability, readability, and time-saving aspects. It also distinguishes between built-in and user-defined functions, providing examples and demonstrating the process with a practical coding exercise in Reebok's Blockly World.

Takeaways

• 😀 Functions in Python are blocks of code that perform specific tasks when called.
• 🔑 Functions help in organizing code by grouping related statements together, making the code more modular and easier to maintain.
• 🍲 The analogy of a recipe for idli is used to explain the concept of functions, where the recipe (function) can be followed (called) multiple times to achieve the same result.
• 👩‍🏫 The importance of functions is emphasized by showing how they can save time and effort by avoiding the repetition of code.
• 📝 The definition of a function in Python uses the 'def' keyword, followed by the function name and parentheses, which may include parameters.
• 🔄 Functions can be called with parameters to perform different tasks based on the input, demonstrating their versatility.
• 🔧 Built-in functions are pre-defined in Python and can be used directly, such as 'print', 'len', 'max', and 'min'.
• 🛠 User-defined functions are created by the programmer to perform specific tasks as needed, enhancing the functionality of the program.
• 📈 The benefits of using functions include increased code reusability, improved readability, and time-saving by avoiding code duplication.
• 🤖 A practical example using a robot in Reebok World is provided to illustrate how defining and calling functions can control actions and simplify programming tasks.

Q & A

What is the main topic discussed in this video script?

The main topic discussed in this video script is functions in Python programming language.

Why are functions important in programming?

Functions are important in programming because they promote code reusability, increase code readability, and save time by avoiding the need to repeat code blocks.

Can you give an example of a real-life analogy for functions mentioned in the script?

The script uses the analogy of a recipe for making idli, a South Indian food, to explain the concept of functions. Just as a recipe can be written down and followed multiple times without repeating the steps, functions in programming can be defined once and called multiple times to perform a specific task.

What are the two major steps involved in using a function in Python?

The two major steps involved in using a function in Python are defining the function using the 'def' keyword and then calling the function by its name followed by parentheses.

What is the purpose of the 'def' keyword in Python?

The 'def' keyword in Python is used to define a function, marking the start of the function's declaration.

What is the term used for functions that are already defined in Python?

The term used for functions that are already defined in Python is 'built-in functions'.

How does defining a function help in reducing the number of lines in a code?

Defining a function helps in reducing the number of lines in a code by allowing you to encapsulate a block of code that performs a specific task and then reuse that block by simply calling the function, instead of repeating the code block multiple times.

What is the significance of indentation in Python function definitions?

Indentation in Python function definitions is significant because it demarcates the body of the function, indicating which lines of code are part of the function's execution block.

What is the difference between built-in functions and user-defined functions in Python?

Built-in functions are pre-defined in Python and can be used directly without any additional code. User-defined functions, on the other hand, are created by the programmer to perform specific tasks as per the program's requirements.

Can a function in Python accept parameters?

Yes, a function in Python can accept parameters. Parameters are specified within the parentheses in the function definition and can be used to pass values into the function to make it more versatile.

What is the purpose of the 'return' statement in a Python function?

The 'return' statement in a Python function is used to send a value back to the caller of the function. It is optional and not all functions need to return a value.

Outlines

00:00

📚 Introduction to Functions in Python

The speaker begins by transitioning from a previous Python project, the Hangman game, to a new topic: functions in Python. The video aims to explain the concept of functions, their necessity, and benefits. A real-life analogy is introduced to explain functions, comparing them to a recipe for making idli, a South Indian dish. The analogy illustrates how sharing a recipe (function) multiple times can be streamlined by writing it down once, emphasizing the idea of reusability and efficiency. The speaker also hints at introducing a new tool in the video that will help viewers become more comfortable with functions.

05:01

🛠 Defining and Using Functions

This paragraph delves into the technical aspects of defining and using functions in Python. The speaker explains the syntax for defining a function using the 'def' keyword, followed by the function name and parentheses. Parameters and return statements are introduced as optional components of a function. The importance of indentation in Python is highlighted. The concept of built-in functions, such as 'print', is contrasted with user-defined functions, which are created as per specific needs. The speaker emphasizes the benefits of using functions, such as code reusability, readability, and time-saving, using the example of a simple greeting function.

10:01

💡 Benefits of Functions and Practical Example

The speaker discusses the advantages of using functions, such as increased code reusability, readability, and time efficiency. A practical example is provided to demonstrate how defining a function can reduce the number of lines of code and make the program easier to understand. The example involves creating a Python file named 'intro.py' and defining a simple function called 'greet' that prints a greeting. The speaker then shows how to call this function multiple times in the program, thereby avoiding the repetition of code.

15:03

🤖 Applying Functions in a Coding Tool

The speaker introduces a coding tool, Reebok's World, to provide a visual and interactive way to understand functions. The tool allows users to write Python code and execute commands to control a robot. Built-in functions like 'move' and 'turn left' are used to give commands to the robot. The speaker then demonstrates how to define a custom function, 'turn right', to make the robot turn right by using the 'turn left' function three times. This practical demonstration helps to reinforce the concept of functions and their application in programming.

20:05

🔄 Defining Custom Functions for Robot Commands

In this paragraph, the speaker encourages viewers to define their own function, 'turn around', for the robot in the coding tool. The function is defined by turning left twice, which effectively makes the robot turn around. The speaker then integrates this custom function into the robot's sequence of commands, demonstrating how it simplifies the code and makes it more efficient. The video concludes with an exercise for viewers to practice defining and using functions, emphasizing the importance of understanding functions in programming.

Keywords

💡Function

In the context of the video, a 'function' refers to a block of code or a set of statements in Python that perform a specific task when called. It is a fundamental concept in programming that allows for code reusability, making the script more efficient and easier to manage. The video script uses the concept of a recipe for making idli as an analogy to explain how a function groups a set of steps to be reused without repetition.

💡Defining a Function

The process of 'defining a function' in Python involves using the 'def' keyword, followed by the function name and parentheses. This is a crucial step in creating reusable code blocks. In the script, the process is explained with the simple example of a 'greet' function, which when called, prints a greeting message, demonstrating how functions encapsulate behavior.

💡Function Call

A 'function call' is the act of executing a function by referring to its name followed by parentheses. This is how the predefined behavior within a function is invoked. The script illustrates this with the 'greet' function, where calling the function results in printing the greeting, showing the practical application of functions in a program.

💡Parameters

Parameters are optional values that can be passed to a function when it is called, allowing the function to behave differently based on the input. The script does not use parameters in its initial examples but explains their concept, noting that functions like 'print' use parameters to determine what to display.

💡Return Statement

The 'return statement' in a function is used to send back a result to the caller. It is optional and not all functions need to return a value. The script mentions that functions can have a return statement to output a value or result of the function's computation, but it also clarifies that this is not mandatory.

💡Code Reusability

The concept of 'code reusability' is highlighted as one of the key benefits of using functions. It refers to the ability to use the same block of code multiple times without rewriting it. The script explains this with the idli recipe analogy and the 'greet' function example, emphasizing the efficiency gained by avoiding repetitive code.

💡Readability

'Readability' in programming refers to how easy the code is to understand. The script points out that using functions can improve the readability of code by reducing the number of lines and providing clear, descriptive function names that indicate the block's purpose, such as the 'greet' function used in the examples.

💡Built-in Functions

The script introduces 'built-in functions' as pre-defined functions in Python that are ready to use without any additional definition. Examples given include 'print', 'len', 'max', and 'min', which are used throughout programming to perform common tasks, demonstrating the convenience and time-saving aspect of these functions.

💡User-Defined Functions

In contrast to 'built-in functions', 'user-defined functions' are those created by the programmer to perform specific tasks tailored to their needs. The script explains how to define such functions using the 'def' keyword and provides examples like the 'greet' and 'turn right' functions, showing how they can be customized for particular behaviors.

💡Indentation

In Python, 'indentation' is syntactically significant and used to define the scope of code blocks, including functions. The script emphasizes the importance of proper indentation after the 'def' keyword and within the function body to avoid errors and ensure the function is defined correctly.

💡Reebok's World

Reebok's World, mentioned in the script, is a tool or platform for learning programming concepts through interactive exercises. It is used as an example to illustrate how functions can be applied in a practical and visual manner, with the script showing how to define and call functions within this tool to control a robot's movements.

Highlights

Introduction to the concept of functions in Python programming.

Explanation of why functions are necessary in programming.

Real-life example of a function using a recipe for making idli.

Discussion on the benefits of using functions in programming.

Definition of a function in Python and its syntax.

Mandatory and optional parts of a function definition.

How to call a function in Python.

Difference between built-in functions and user-defined functions.

Practical demonstration of defining and calling a function.

Introduction of a new tool for learning functions: Reebok's World.

Using built-in functions in Reebok's World to control a robot.

Defining a custom function 'turn right' in Reebok's World.

Advantages of functions in terms of code reusability and readability.

Practical exercise on defining a 'turn around' function.

Final thoughts on the importance and utility of functions in programming.

Transcripts

so in the series of learning Python

programming language in the previous

video we have seen a project we have

created a project Hangman game right so

from this video I'm going to start a new

topic that is functions in Python right

and this will in this video we'll be

discussing basic about function what is

a function why basically we need a

function this answer of this question is

very important y functions what are the

benefits of using function how to define

a function what are different types of

function

right with the help of real life example

I'll tell you what is function and with

the help of program also practical also

I will show you and I will introduce you

with a new tool also in this video

after using that tool you will be you

know you know uh very friendly you can

say with functions

right it would be very easy for you guys

maybe someone of you are aware about

functions they have learned other

languages CC Plus for Java but let's

start this with a real life example

suppose I know I know a recipe I know

how to make idli one of my favorite from

South Indian food actually

and suppose one Sunday my friend came to

me came to visit me and I made idli for

them

and she was like oh wow Italy like they

they are so delicious and amazing so

she asked me the recipe for that idli

and I told her like like this

even to be very Frank I don't know what

is the recipe but let's take let's

assume I know so Suppose there are these

five or six or seven steps one two three

four five six seven steps

in the recipe so I told her these seven

steps right maybe uh on next day or on

another friend came to me and

She also asked me for the same recipe

because I made idli again

because in this I am expert you can say

so I told her the same recipe like this

maybe every Sunday or every after two to

three days someone is coming to me and I

am telling them the recipe I am

repeating these seven steps again and

again I'm telling them the recipe right

so

what I can do rather than this what I

can do now I'm feeling very frustrated

after telling the recipe again again and

again so what I can do I can just write

down this recipe on a paper right

and like r e c i p e

recipe

of idli you can say making idli right

and whenever anyone comes to me and asks

for the recipe I just hand over this

piece of paper too

damn right

so yeah it is going to say what what is

the benefit my energy and my time

right I have just

grouped these steps

in US

you can say an entity this is an entity

on a paper and I'll just hand over that

paper too

whoever is going to ask me the recipe

about the recipe

right so yeah this is beneficial for me

right same

we have some function like uh in

programming also we have to do something

like some task again and again

right suppose let's take one example

and see if you take one more example

like we human being also we are

performing different different

functionality we are multitasker like

let's take a female as a mother as a

wife as a daughter as a working woman

and many functionalities are there

right so different different

functionalities are there for the same

entity for the same person right means

like if you are in front of your student

you are working you are you know uh you

know your responsibilities work you know

acting as a teacher right if you are in

front of your

children then your responsibility means

your functionality is your working as a

mother something like this

so whatever is in front of you according

to that you have to perform your task

right for different different inputs you

are performing your specific task

right so like this example also you can

relate with the functions let's take uh

this example if in programming also like

two lines there are two lines simplest

example I am taking like print hi and

like Jenny

and good morning

like this

I want to print these two lines again

and again in my program like perform

some specific task then execute these

line then perform some specific task

then again I want to

before I want to you know greet like I

want to uh print hi Jenny good morning

then again perform some specific task in

the same program again I want to perform

these two lines perform some specific

tasks again I want to greet like hi

Jenny good morning right in program

maybe 50 times so 50 times you need to

write down these two lines so rather

than this what we can do rather than

repeating the two lines again and again

what we can do the same thing

just wrap up this thing

here

like print these two lines print

then Jenny and

good morning these two lines here

right and just call it what I'm calling

this a recipe right so it's like once

you're functioning so let's call this

thing what a function name greet

and whenever you want to execute the

these two lines then just call this

function greet greet greet so rather

than writing these two lines again and

again just have to write down simple

function name greet that's it

right now I'll tell you how to define a

function how to call the function there

are two major steps basically first of

all you have to define a function then

you have to call the function right

so now I hope you got it what is

basically a function function is just

what a block of statements or block of

code this is just a block of code this

is just a block of code or statement

these are statements

right

which perform some specific task

when it is cold it is going to perform

those tasks only when you are going to

call that function these lines are very

important so when it is code so function

is a group of

you can say it's or you can say block of

statements or block of code which is

going to perform a specific task which

perform a specific task when it is

called that is function definition very

simple right now how to define a

function let me tell you two steps I

have told you first Define a function

then call the function right so how to

define a function simple what is the

syntax you will write down this def

keyword def then

here you will write down your function

name any name you can take like add

subtract grid any function name display

anything

these parenthesis then colon or in these

parenthesis

if you want to pass you can pass

parameters right then here we have

here we have function body or let me

just write down this thing here we have

function body

and after that we have like return

return statement

return keyword and then some expression

or whatever you want to return so this

is what the complete one

it is not necessary to pass parameter

every time it is not necessary that

every function is going to return

something so this line is optional this

one these parameters are optional but

the mandatory part is to define a

function def keyword function name these

parenthesis maybe these are empty this

colon and then function body

right these are important these are you

can say mandatory part if you are going

to define a function parameters return

expression these are optional part right

and this this this should be indented

right see I have there are some space

at the beginning of these two lines so

they should be indented otherwise it

will give error

right so this is you are going to define

a function how to call the function then

just write down the function name

whatever the function name and

these parenthesis if if you have passed

some parameter if you use some parameter

when you are defining a function then

you have to pass those parameters here

One Two Three or how many parameters you

have

there are no parameters just function

name and these parenthesis this is what

you are going to call the function

right

now

and function will only work when you are

going to call that function only

definition of this function this is not

going to work

you have to call that function

right like me as a teacher

so whenever I am in front of my student

right in front of my class

then only I lacked as a teacher means at

that time students are calling me you

can say they are calling me so at that

time only I'll work as a teacher right

so you have to call that function

right now there are two types of

function built-in function plus user

defined function so built-in functions

are so built-in functions are already

defined in Python already pre-coded or

already defined right you don't need to

write down any code to define those you

can only use the you can directly use

those function like simplest one is

print in every program we use this

function

this is already defined in Python so you

just have to use that function just

print in these parenthesis whatever you

want to print that you can pass here we

pass that parameter the argument right

built in like print we have Len function

we have used this is also built in Max

Min and type also we have used

right

so many functions are there you can also

write down few built-in function in

comment section

now next a user defined a function user

defined means you have to Define user

will define those functions as per our

need

like whatever you want like I want to

define a function of addition of two

number

so according to my head I'll Define a

function the statement the code I'll

write according to myself right and how

to define that I have told you how to

call that I have told you

right

now let's see this thing with the help

of example and I will introduce you with

a new tool also then you will get it

better what function is and why we use

it and now the the benefits or advantage

of using function is what

I guess now you got it what can be the

benefits of using the function

definitely your

code becomes

more reusable rather than writing these

two lines again and again in the program

just call the function so it means we

are reusing these two lines so code

reusability will increase

the code would be more readable right

because obviously if you call a function

if you use functions then the number of

lines in your code will also is going to

decrease will be less and if less line

of lines of code then your code would be

more you can say readable

right

so these are few you can say and it will

be time saving also right just Define

one time and use reuse those thing again

and again so it would be

time saving for you right let me just

show you this thing with the help of

practical we'll see a program on

functions okay so let's create a new

file here for functions and

functions like intro Dot py

right

and

let's define a function depth how to

define depth let's take a function

suppose grid

right colon and here it should be

indented and there I just want to print

high in one line and suppose here I want

to print only gen

these two lines

so now

this is definition of the function we

are not passing any parameter because

these are optional we are not returning

anything here right so

now here what we can do how to execute

this function if I run this code see

suppose we have defined a function

and let's let's run this code

see it is not printing anything the

screen is blank right why so because

to execute the function

I have told you in the definition the

function is a statement or block of

statement block of code which performs

some specific task when it is called so

you have to call the function have to

call the function just

name of the function grid that's it this

is calling of function now let's run

this and this time it will print hygiene

so if you want to print this multiple

times

so again I want to call grid again like

read three times so these two lines will

be printed three times in your program

in the output see hi Jenny hi Jenny hi

Jenny right

so this is how the function will work

now let me just introduce you with a new

ah like tool we have Reeboks World our

website is there okay for that you can

directly search for like python coding

free box world so

first we'll take this example the second

link alone World info python blocky this

keep editor visible right let's run this

and this is going to load

right so here this type of thing would

be opened here the project name is C

along right

okay now see the python code here we can

write down python code so see here we

have some functions like when you click

on this Rebox keyboard then you will get

some function like you can say command

move turn left take put these kind of

commands you can give these commands to

this robot and it will perform according

to your given command so here I have

written one command like move here we

have one command move movements it will

move further One Step only so how to run

this there's a play button right here

just click on that and see

it has moved one step ahead so last

instruction completed so if you want to

move this three steps or two steps then

just use this function again move

or maybe three times move

and now if you want to go back here just

click on this just go back this one and

just click on the play so see it has

moved three steps the robot so last

instruction completed right so here we

can write down our python codes we

haven't written till now we are still

you we are using those uh you know

inbuilt function only we have we haven't

defined our own function till now but we

are going to Define right

if one by one if you want to execute the

instruction suppose first instruction

instruction first and second and third

so you have to click on this one step

through button step

click one then

see it is going to show this one line

would be executed move

see like this

again move again click move

three line would be executed and that's

it last instruction completed so let's

back here

and okay

turn left there is one function use this

turn left just click on that and it

would be here turn left

or rather than first turn left first we

move this robot like three times and

then we use the function

turn left

not at the starting

so if I run this code here so three step

then turn left

see turn left the robot has turned left

this weight is going then turn left this

side

and again

if I

after turn left if I use the move

function again three times and if I run

this again

see now this would be executed move

first three times turn left and move

again

three times right but there is no see

there is no turn around or turn right

function here

right only turn left is there now if you

want to

here

command the robot to turn right then how

you leave that thing

so Define your own function turn right

function at this point of time if I want

to give the command to this robot turn

right

then how will you now you have to Define

your own function now pause the video

and Define your own function

okay how we are going to Define

def keyword function name I am taking

turn right

parenthesis colon and now the definition

it should be indented right

now turn right means simply at this

point of time if this robot we give this

robot three times turn left command then

it would be

automatically at the last

ultimately turn right command would be

executed so three times turn left so now

this is a turn right function now now if

I call that this function here

turn right

and suppose again

move

One Step move and if I run this let me

just stop this just click on this

reload button and play

like this

right turn right and then one move but

we have defined our own function suppose

if you want to

execute this if you want to command

command this uh you know uh

robot something like this okay the same

thing then

it has to move downward three step

right again and then

simply

the face would be in this in this

Direction only this direction forward

Direction only right so how we are going

to give this this this command see now

at this point of time also

for going downward you have to give the

command obviously turn right like this

we are facing then at this point of time

means turn right right and if suppose

you haven't defined this function

then for turn right you have to write

down this turn left three times

so here rather than turn right you have

to write down these

three times

then again move then again turn right so

again write down these three commands

turn left command here like three times

here there should be no indentation

right

now three times move

right and then finally

turn left

right

this would be the case if we are not

using the function turn right we haven't

defined the function so let's stop this

and now let's run this

so now you are repeating these turn left

and turn left these three lines again

and again whenever you want to give the

command to the robot turn right then

three times you have to write down turn

left again and again

so better to define a function so that's

exactly we have done just Define a

function turn right and rather than

these three lines

just use one line turn

right that's it rather than these three

lines

turn

right

just one line

so yeah this is going to reduce the

number of lines in your code when you

are using function code reusability will

increase and as well as code readability

will also increase right this is also

going to perform the same task

one by one we are going to run this now

this step through option

let's run this once click then again

click

then this move command would be executed

then second move again run again

turn left again again again click on

that now see cursor is a

here at this function turn right now

click on the step function now person

would be here

in the definition of this function so

first turn left

again second turn left again third turn

left would be performed now that's it

now we are we are turning we have turned

right this robot then move then again

turn right then again function would be

cold see the cursor is again the control

is again here within the function

then three times turn left and then move

then this move then this then again turn

left and that's it

right

so this is beauty of function you can

say now one exercise for you is

turn around

there is no function turn around here so

you have to Define your own function how

to turn around

let's suppose move this robot three

times here

three times forward then turn around

then three times backward the same

position how you will Define your

turnaround function pause the video and

try this out

okay I hope you have done this how to

define turn

I think this is very simple if you have

done this turn left turn around is very

simple

just two times turn left and that's it

this should be turn around two time turn

left only right so let's

here we will do that thing after turning

left at the final time then we will call

turn

around function

and then again

move

right let's run this and see what output

you will get

C

turn around and then back one step

so this is what we can Define our own

function turn around turn right function

so I hope you got the basics of

functions why we need functions use of

function benefit of function and all now

in the actually we'll see one more

coding exercise on function now this is