#21 Python Tutorial for Beginners | For Loop in Python

Summary

The video explains the difference between while and for loops in Python. While loops iterate based on a condition, for loops iterate through sequences like lists and strings. The script shows how to print list values with a for loop and use the range() function to print sequences of numbers, including in reverse order. It demonstrates how to use an if statement inside a for loop to selectively print values, like printing numbers not divisible by 5. The next video will cover printing patterns using nested for loops.

Takeaways

• 😀 While loops are used for uncertain iterations, for loops work with sequences like lists, tuples, and strings
• 👉🏻 For loops automatically iterate over the elements of a sequence, no need to manage iteration variable and conditions
• 📝 Use 'for i in sequence:' syntax and indent the code block to use for loop
• 🔢 Can iterate over numeric ranges using the range() function - specify start, stop and step size
• ❗ Range excludes the stop value, so make the stop value 1 more if you want to include it
• 🔄 Set step size as -1 in range() to iterate in reverse order
• 🤝 Use if condition inside for loop to filter values while iterating
• 🎯 For loops can be nested inside other for loops similar to while loops
• 📜 String, lists, tuples can directly be used in place of a variable in for loop syntax
• 👍 For loops clean way to iterate as alliteration managed automatically

Q & A

What are the two types of loops discussed in the video?

The two types of loops discussed are the while loop and the for loop.

How does a for loop differ from a while loop?

A for loop works with sequences like lists, tuples, and strings and automatically iterates through the values, while a while loop depends on a condition and we have to manually increment/decrement the iterating variable.

How can we print values from a list using a for loop?

We can print values from a list using a for loop by iterating through the list element by element using the iterating variable of the loop.

What is the syntax for using a for loop?

The syntax is: for var in sequence: #loop body

How can we print numbers from 1 to 10 using a for loop?

We can print numbers from 1 to 10 using the range() function along with a for loop. For example: for i in range(1, 11): print(i)

Can we use if statements inside a for loop?

Yes, we can use if statements inside a for loop to add conditional logic and filtering.

How can we print numbers in reverse order using for loop?

We can print numbers in reverse order by using range() with negative step size. For example: for i in range(20, 10, -1)

What collection types can be used with a for loop?

For loops can be used with lists, tuples, strings, and any other iterable objects in Python.

Can we nest for loops in Python?

Yes, we can nest one for loop inside another for loop in Python to create nested iterations.

What patterns will be discussed related to loops in the next video?

In the next video, some patterns related to printing shapes and structures using loops will be discussed.

Outlines

00:00

📝 For Loops in Python

This paragraph explains how for loops work in Python. It iterates over sequences like lists, tuples, and strings to print values one by one. It is easier than using while loops and index values. The syntax includes the for keyword, a variable to represent each element, the in keyword, and the sequence to iterate over. The range() function can also be used with for loops to print a specific range of numbers, including options to set start, end, and step size values.

05:01

🔁 Using Range and Conditions in For Loops

This paragraph continues discussing how to use for loops in Python. It shows how to print numbers in reverse order using range() through setting negative step values. It also covers using an if condition inside the for loop to selectively print values, like only printing numbers not divisible by 5 in a given range. This demonstrates the flexibility of using logical conditions within for loop iterations.

Keywords

💡for loop

A for loop is a programming construct that repeats a block of code a specified number of times. In Python, it iterates over a sequence like a list or string, assigning the values to a loop variable one by one. The video shows how to use a for loop to print the elements of a list individually, instead of printing the whole list at once.

💡range

The range() function in Python generates a sequence of numbers that can be used to perform repeated actions a set number of times in a for loop. As shown in the video, range() lets you specify the start, stop and step size for the sequence of numbers, including counting backwards.

💡iteration

Iteration means repeating a process over and over. In a Python for loop, iteration happens automatically based on the sequence it's looping over. We don't have to manually control the iteration like in a while loop.

💡sequence

A sequence in Python refers to an ordered collection of elements that can be looped over, like a list, tuple, string, etc. For loops work by iterating over the elements of a sequence in order.

💡loop variable

The loop variable in a Python for loop is a temporary variable that gets assigned the value of each item from the sequence in turn. It gives access to the individual elements inside the loop body. Here, the loop variable 'i' holds values from the list 'x'.

💡loop body

The loop body contains the code that needs to be executed repeatedly in the loop. It must be indented properly to associate it with the for loop. Here, the print statement printing the loop variable is inside the loop body.

💡modulo

The modulo or mod operator (%) gives the remainder when one number is divided by another. It's used here inside the loop to check if 'i' is divisible by 5, to print only those numbers not divisible by 5.

💡nested loops

We can have loops inside other loops in Python, which is called nested loops. The video mentions how a for loop can be nested inside another for loop, though it does not demonstrate it.

💡loop control

Loop control refers to controlling how a loop executes by skipping iterations or stopping the loop altogether. Here, the if condition inside the loop serves as loop control by skipping numbers divisible by 5.

💡indentation

Python uses indentation instead of braces `{}` to denote blocks of code like loops. The lines inside the loop body have to be indented consistently for the loop to work correctly. Improper indentation causes errors.

Highlights

For loops work with sequences like lists, strings, tuples

The variable 'i' refers to each element of the sequence in the for loop

For loops automatically iterate through the sequence, unlike while loops

Can print sequence elements one by one using a for loop

For loops can directly iterate over the sequence without needing a separate iteration variable

The range() function generates a sequence of numbers that can be iterated with a for loop

Range allows controlling start, end, and step size of numeric sequence

For loops can go in reverse order using range() with negative step value

If statements can be included inside for loops for conditional iteration

For loops can be nested inside other for loops

Will cover some pattern printing examples with for loops in next video

For loops are useful for iterating over sequences and programmatic control

For loops avoid needing manual increment logic like while loops

The iteration variable moves automatically through the sequence

Can filter iteration with conditions inside the for loop

Transcripts

[Music]

welcome back aliens my name is Ivan

vetti and let's continue this series on

Python so in the last video we have

talked about loops right and

specifically it was a while loop in this

video we'll talk about for loop

so while loop and for loop they both are

loops right but then the working is

different in fact normally when we talk

about while loop it is for certain 2

iterations and it is positon conditions

so if ever the while loop we specify a

condition but that's not the case with

father because in for loop it normally

works with sequence whatever sequence

I'm talking about think about least

think about tuple think about string so

what I'm basically talking about is

let's say if you have a laced here and

in this list AHA certain values it can

be any random value let's say my name

Naveen 65 and if I say they'd say 2.5 so

these are I have this values one is

string one is integer and when his float

doesn't matter what type of value you

have there I want to print this values

it's really easy actually you can simply

say print and you can print the value of

x this will work okay let me just run

this code and you can see record the

output but what if you want to get the

output individually I want to print the

values one by one so in this case you

will be using a for loop now for loop

works so we have to say for then we have

to use a variable with this we will say

this time I now I represents one element

of this list at a time so example

initially I will refer to Naveen then I

will refer to 65 then I will refer to

2.5 one by one so you have to say for I

in X so one by one it will fetch the

value and again this is a suit so you

have to use a code in there and you can

write lines of statements again the

point is you need to make sure that you

use a proper indentation so I will be

printing the value that's it

I will printing the value of I that's it

said those there's no iteration unlike a

while here so we don't the enjoys the

variable we don't take the condition and

we don't increment or decrement by

ourselves which will be done by for loop

itself this which is smart right so now

if I run this code you can see record

the values one by one so yes if you want

to print all the values from at least

use for loop so for loop normally can be

used with

sequence example list which you have

worked with now all a string let's say

you have a string here let's say the X

is not at least now it is a simple

string which is Naveen and then I want

to print the value of this one by one so

one way is you can use an array right so

we can use a while loop here as well and

then you can use that square back and

you can specify index index values

otherwise if you run this code you can

see this is how you're for the works so

what it will do the value of I first

will have N and that will have a let me

let me just do that again the thing

which we are doing from a long time

which is debug so I'd like and say debug

let's trace it so if i trace you can see

the value of x is naveen and the value

of i is and now i'll give you fire

repeat if I said next iteration you can

see the value of I it will become a and

the next iteration value of I becomes V

the value of I becomes I and then value

of I becomes n so that's moving for you

and you're printing all the values right

so if I see the console you got all the

run is one by one right of course I

forgot to one do one more so you got

live in that so that's the advantage of

using for loop oh can I use for loop

with something else yes we can example

we can also use this with tuple or we

can use with say but then we have one

more example in you can do you can

specify the list itself okay instead of

having a different variable you can have

your list here even that works here so

you have two six Paul and if I done this

code you can see we got one by one so

you can have your list yet itself so

syntax is you mention for then you say I

in and then you mention the collection

or the sequence it can be a list it can

be a string everything works in fact

what if I want to print the values from

1 to 10 because of course why we can do

that

we can do that in while loop can we do

it here and this is yes for that we have

to use range if you remember in sequence

we have talked about range in range you

can specify 10 what it means it means

start from 0 and end at 9 so in total we

have 10 values and if I have this code

you can see record and 0 to 9 so we got

0 and then it ends at 9 so in total we

have 10 values so we can use range as

well and using this range you can

perform certain operations in fact in

rain

you can actually start from different

values it's I don't want to print from 0

to 10 I want to print from let's say 11

to 20 in that case you would say hey I

want to start from 11 I want to end at

2070 so we want 20 included right so

we'll say 21 and every iteration will

have 1 so it will be 1 by 1 iteration so

if I say run so you can see we got

values from 11 to 20 so you have to

mention three things starting point

ending point and the iteration it will

be difference would be 1 or 2 example if

I say this is 2 in this case so look at

the values now it will be different

values 11 13 15 17 and 19 so if there's

a difference of two if I say 5 you can

see we got 11 and 16 that's it so this

is how you specify the gap there what if

you want to print in Reverse let's try

can I start with 20 and if I end at 11

if I run this code it will give you it

is giving you nothing because it always

goes in ascending order we have to

mention go in reverse order so you have

to say minus 1 so it will start with 20

and then 1918 and it wasn't that way so

you can see we got from 20 to 12 but

there's a problem you have to make sure

that it goes till 11 right so you have

to because the value 11 is excluded so

we have to use 10 so that it will

include 11 that you want this again and

it works so this is how you can reuse

range and this how you can use for loop

now in fact we can do one more thing so

you can see if we have a range of 20 and

then I'm printing the value of I in fact

I will just go I will start with 1 so

much from 1 to 20 so I will inclusive I

will make sure it is 21 so that it will

include 20 and the iteration would be 1

or even if you don't mention that that's

fine if I say print value we can see it

just 1 to 20

what I want is so every time the value

which is a divisible by 5 it should not

get printed okay so I want that so I

want to print only when the value is not

user by 5 so we can use a inside phone

right so we can do that so we can have

if condition inside for if you want to

if you have if you want to have that

condition so you can say if I mod 5 is

equal to equal to 0 don't print

otherwise you can print okay but how can

I do that so what we can do is we can

say not equal to so print only when it's

not equal right so we can do that so

print only when it is not equal to say

fine on this code if I say

oh we got an error because I missed

something and I'm also using brackets

because I have this habit of working on

Java so it's the anyway it's optional in

Python so let's run this and you can see

we got we got one and regard for you can

see we don't have five there because we

are taking about the condition so yes we

can write it inside of four so since we

had if inside fault we can also have

fall inside of four which is a

straightforward loop but then we will

not be doing that here in the next video

we'll play with some patterns you know

we'll try the dorsum patterns and we'll

try to understand how do we do that

so in the next video it will be fun so I

hope you are enjoying the series it

means the comment section and dukey like

button if you're enjoying it I'm

watching everyone bye

you