This tutorial provides a comprehensive introduction to Python programming, covering fundamental concepts from installation and basic syntax to data types, control flow, and data structures, designed for absolute beginners aiming for applications in data science, machine learning, or web development.
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in this python tutorial you're going to
learn everything you need to know to
start programming in python if you want
to learn python programming for data
science machine learning or web
development this python tutorial is the
perfect place to learn python you don't
need any prior knowledge in python or
programming in general i'm going to
teach you everything from scratch i'm
mosh hamadani and i've taught millions
of people how to code through this
channel if you're new here make sure to
subscribe as i upload new videos every
week now let's jump in and get started
all right before we get started let me
give you some ideas about what you can
do with python that's a very common
question python is a multi-purpose
programming language so you can use it
for a variety of different tasks you can
use python for machine learning and ai
in fact python is the number one
language for machine learning and data
science projects python is also very
popular in web development using python
and a framework called django you can
build amazing websites here are five
websites powered with python and django
youtube instagram spotify dropbox and
pinterest you can also use python in
automation with python you can save your
time and increase your productivity by
automating repetitive tasks so why are
you learning python are you learning it
for automation for data science or web
development let me know in the comment
all right the first thing i want you to
do is to head over to python.org to
download the latest version of python so
you go to downloads and select the
here in your downloads folder you should
see this package simply double click it
you're going to see this python
installer if you're on windows you will
see this checkbox over here add python
to path make sure to check it it's
really important otherwise you're not
going to be able to follow this tutorial
simply click on continue again
again
one more time
i agree with the terms
and install the latest version of python
now here you need to enter the username
password of your computer so
so
next you need to install a code editor
we use a code editor to write our code
and execute it the most popular code
editor for python is pycharm you can get
it from jetbrains.com pycharm
pycharm
so on this page
click on download
you should see two different editions
one is the professional edition which is
commercial and we also have this
community edition which is free and open
source so we're going to download the
now in your downloads folder you should
if you're on windows you're going to see
an installation wizard so simply click
on the next button until you install
pycharm if you're on a mac you need to
drag this pycharm and drop it onto the
now
let's open it
the first time you open pycharm you have
to configure a few settings we don't
want to spend time on this so over here
we're going to click on skip remaining
and set defaults
now let's create a new project
over here we can specify the location
and the name of our python project so
let's append hello world to this path
this is where our python project is
going to be saved so let's click on create
in this window you can see the content
of our project so here's our hello world
project currently we have only one
folder inside this project that is vn
which is short for virtual environment
we'll talk about virtual environments in
the future so currently we don't have
any python files inside this project a
real application can consist of tens or
hundreds or even thousands of python
files so let's right click on the
project name
and go to new python file we're going to
now we can collapse this project window
by clicking on this icon so now we have
more space let's write our first python
code we're going to write print all in
lowercase then add parentheses
then add quotes either single quotes or
double quotes
and inside this code we're going to
write hello world
so this is what we call a string a
string means a string or sequence of
characters in simple words that means
textual data so in python and in many
other programming languages whenever
we're dealing with textual data we
should always surround our text with quotes
quotes
in python we can use single or double quotes
quotes
now this print you see here is a
function built into python and we can
use it to print a message on our
application window so let me show you
how to run this code
on the top we go to the run menu and
then select run
note that there is a shortcut associated
with this command i always use shortcuts
because they increase my productivity so
let's click on this
now select app
and over here
you can see this little window this is
what we call the terminal window and it
shows the output of our program
so here's the hello world message
printed in the terminal window now as
you learn more python you will learn how
to build applications that have a
graphical user interface that's an
advanced topic so for now let's not
alright now let's talk about variables
we use variables to temporarily store
data in a computer's memory for example
we can store the price of a product or
someone's name their email their age and
so on let me show you so
to declare a variable we start by typing
a name for that variable let's say age
then we add an equal sign
and then we type a value let's say 20.
so with this we're storing the number 20
somewhere in our computer's memory and
we're attaching this age as a label for
that memory location so now we can read
the value at this memory location and
print it on the terminal so instead of
printing hello world we want to print
the value of the age variable
so i'm going to delete what we have
inside parenthesis
and type age note that i'm not adding
quotes because if i run this program
we'll see the text h on the terminal we
don't want that we want the value of the
age variable so let's remove the quote and
and
print the value of the age variable
now here on the toolbar you can click on
this play icon to run your program or
you can use the shortcut that i showed
you in the last video so the shortcut is
over here on a mac that's ctrl shift and r
r so
so
there you go
now you can see the value of the age variable
variable
now we can also change the value of a
variable for example on line 2
we can set 8 to 30.
now when we run our program
we see 30. so as you can see our program
gets executed from top to bottom
so this is how we can declare and use a
variable now let's look at a few more examples
examples
so i'm going to declare
another variable called price
and set it to 19.95
so in python we can use numbers with a
decimal point or
whole numbers we can also declare a
variable and assign it a string value so
let's say first underline name so if you
want to use multiple words in the name
of a variable we should separate them
using an underscore this makes our code
more readable see what would happen if i
didn't use this underline
this is not easily readable so we always
separate multiple words by an underscore
now we set this to a string so we can
use single quotes or
double quotes let's say march
we also have a special type of value
called a boolean value which can be true
or false that is like yes or no in
english let me show you so i'm going to
declare another variable called is
online and set it to true
we could also set it to false what we
have here is called a boolean value
now note that python is a case sensitive
language so it's sensitive to lowercase
and uppercase letters in this case if i
use a lowercase f
we can see an error over here because
this is not recognized in python
so false with a capital f is a special
keyword in python that represents the
boolean false value
so this is how we can declare and use
variables in python
all right now here's a little exercise
for you
imagine we want to write a program for a
hospital so we're going to check in a
patient named john smith he's 20 years
old and is a new patient i want you to
declare a few variables to store these
values use the comment box below to
in this tutorial i'm going to show you
how to receive input from the user so in
python we have another built-in function
called input we use this to read a value
from the terminal window let me show you
so we add parenthesis
then we type in a string here we can
type a message like what is your name we
had a question mark followed by a space
you will see why we need this space in a
second so let's run this program
we get this message now we have to enter
a value so we click over here
now you can see that the carrot is
separated from the question mark this is
because of the white space that we added
over here
so now we have to type a value let's say
john when we press enter
this function will return the value that
we entered in the terminal window so we
can get that value and store it in a
variable so let's declare a variable
called name and set it to the return
value of the input function
now we can print a greeting message for
this user so we use the print function
we say hello
we had a space
now after the string we want to add the
value of the name variable so we use a
plus sign
and then type name
what we are doing here is called string
concatenation so we're combining this
string with another string
now let's run our program and see what
happens so what is your name mosh
mosh now
now
we get this message hello mosh
so this is how we can use the input
you'll learn about the three types of
data in python we have numbers
strings and booleans now there are times
you want to convert the value of a
variable from one type to another let me
show you so we're going to use our input function
function
to read the user's birth year so enter
your birth here
now this input function is going to
return a value so we can store it in a
variable called
birth underline year okay
okay
now let's write code to calculate the
age of this user so we write an
expression like this currently we are in
the year 2020 so 2020 minus
birth year
this expression or piece of code is
going to produce a value so once again
we can store that value in a variable
let's call that variable age
now let's print age
on the terminal
let's run our program and see what happens
happens so
so
my birth year is 1982.
enter oops our program crashed so
whenever you see this red message that
indicates an error so this error
occurred in this file
that is our app.pi on line two
right below that you can see the piece
of code that generated this error
so that is this expression 2020 minus
birth year now below that you can see
the type of error so here we have
unsupported types for subtraction
we have int
and stir what are these well this end is
short for integer and that represents a
whole number in programming so
2020 is an example of an integer
now birth year is an example of a string
because whenever we call the input
function this function would return a
value as a string even if we enter a
number in other words when i entered
1982 this input function returned a
string with these characters 1982 so
this string is different from the number
1982 they're completely different types
so in this case
let me delete these lines
the reason we got this error is that we
try to subtract a string from an integer
so our code looks like this 1982
1982
now python doesn't know how to subtract
a string from an integer
so to solve this problem we need to
convert this string to an integer
now in python we have a bunch of
built-in functions for converting the
types of our variables so
we have this end function
we can pass our burst here to it
and this will return the new numeric
representation of the birth year
so to solve this problem
we need to replace
the string
with the end function
so let's see what's going on here on the
first line we call the input function
this returns a string
on the second line we pass the string to
our end function the in function will
return the numeric representation of the
burst year then
then
we subtract it from 2020 we get the age
and store it in the age variable now
let's run our program so
so 1982
1982
and there you go i'm 38 years old
so this is how the in function works now
we also have another built-in function
called float that is for converting a
value to a floating point number a
floating point number in python and
other programming languages is a number
with a decimal point so
10 is an integer and 10.1 is a float
so we have int we have float and we also
have bool for converting a value to a boolean
boolean
and finally we have stir for converting
a value to a string so these are the
built-in functions for converting the
type of our variables
now here's a little exercise for you i
want you to write a basic calculator
program so here we have to enter two
numbers we can type a whole number or a
number with a decimal point
and then our program will print the sum
of these two numbers
so pause the video spend two minutes on
all right first we're going to call our
input function to read the first number
we get the result and store it in a
variable called first
now let's declare
another variable called second and read
the second number now
now
we calculate the sum
so that is first plus second
now let's see what happens when we print
sum on the terminal
so i enter 10 and 20
but instead of 30 we get 10 20. this is
because we're combining or concatenating
two strings so
as i told you before the input function
returns a string so
this line will be equivalent to first
equals 10. we're dealing with a string
not an integer similarly
similarly
second is going to be
20 as a string so when we combine two
strings 10 plus 20 will get
10 20 because we're dealing with textual
data okay so to solve this problem
we need to convert the values we read to
their numeric representation so over here
here
we're going to pass
first to our int function
and here as well
now let's run our program
so we enter 10 and 20 we get 30. what if
we enter a floating point number so 10.1
and 20.
we got an error
so to solve this problem
we need to treat both these values as
floats so instead of the in function
we're going to use the float function
now let's run our program one more time
we enter a whole number and a floating
point number so the result is correct
now let's add a label over here so sum is
is
plus sum
let's run our program
one more time 10 and 20.
once again we got an error the error is
saying that python can only concatenate
strings not floats to strings
so on line four we have a string we're
concatenating this with a float because
the result of this expression is a
floating point number we're adding two
floats so the result is a float as well
so python doesn't know how to evaluate
code like this
it doesn't know how to concatenate a float
float
to a string to solve this problem
we need to convert sum to your string so
this is where
we use the stir function
now let's run the program again so
10 plus 20.1 and here's the result
and one last thing
in this example i'm calling the float
function at the time we want to
calculate the sum of these two numbers
but this is not a requirement we can
call the float function
over here so this input function returns
a string we can pass that string to our
float function take a look so float
parenthesis like this
so the value that we're passing to the
float function is the value that is
returned from the input function similarly
similarly
we call the float function over here now
now
we can change this expression to first
plus second that is another way to write
this piece of code
so type conversion is important in
python and other programming languages
there are times you need to convert the
in this tutorial i'm going to show you a
bunch of cool things you can do with
strings in python so let's start by
declaring a variable called course
and set it to python for beginners
beginners
now this string that we have over here
is technically an object an object in
python is like an object in the real
world as a metaphor think of the remote
control of your tv this remote control
is an object and it has a bunch of
capabilities it has a bunch of buttons
for turning your tv on turning it off
changing the volume and so on now in
this program this course variable is
storing a string object this string
object has a bunch of capabilities so if
we type
course dot you can see all the
capabilities available in a string
object these are basically functions
that you can call just like the print or
input functions the difference is that
the print and input functions are
general purpose functions they don't
belong to a particular object but the
functions you see over here are specific
to strings now more accurately we refer
to these as methods so when a function
is part of an object we refer to that
function as a method
so let's look at a few examples here we
have a function or a method called upper
and we use that to convert a string to
uppercase so if we print course.upper
course.upper
and run this program they can see our
course in uppercase
pretty useful
now what you need to understand here is
that this upper method does not change
our original string it will return a new
string so right after this if we print course
course
you can see that our course variable is
not affected so the upper method returns
a new string
now similarly we have another method
called lower for converting a string to
lowercase we have a method called find
to see if our string contains a
character or a sequence of characters
for example here we can pass y
y
and this will return the index of the
first occurrence of y in our string so
in python the index of the first
character in a string is 0. so here we
have 0 1 2 3 4 and so on so when we run
this program you're going to see one on
the terminal because the index of y is
1. take a look first i'm going to delete
this line we don't need it anymore also
let's do this line let's run the program
now as i told you before python is
sensitive to lowercase and uppercase
letters so if i pass an uppercase y here
this find method returns negative 1
because we don't have an uppercase y in
this string we can also pass a sequence
of characters for example 4. so this
will return the index of the word 4.
take a look
so it's 7.
now there are times we want to replace
something in a string with something else
else
to do that we use the replace method replace
replace
so we can replace 4 with
with
a string containing the number 4. take a look
look
so python for beginners obviously
obviously
if you look for a character or a
sequence of characters that don't exist
in our string nothing is going to happen
for example if we try to replace x with
4 obviously we don't have x here so
nothing is going to happen
also just like the upper method the
replace method is not going to modify
our original string so it's going to
return a new string this is because
strings in python and many other
programming languages are immutable we
cannot change them once we create them
whenever we want to change your string
we'll end up with a new string object in memory
memory
now one last thing i want to cover in
this tutorial there are times you want
to see if your string contains a
character or a sequence of characters
one way to do that is using the find
method that we talked about so let's see
if our string
contains python
now when we run this program
that is the index of the first
occurrence of the word python in our
string now in python we can also use the
in operator so we can write an
expression like this
we type a string
python then we type in this is a special
keyword in python this is what we call
the in operator
so after that we type the name of our variable
variable
so with this expression we're checking
to see if we have python in course as
you can see python code is very readable
it's like plain english so when we run
this program
instead of seeing the index of the first
occurrence of python we see a boolean
value this is more desirable in a lot of cases
cases
next we're going to look at arithmetic operations
in this tutorial i'm going to show you
the arithmetic operators that we have in
python these are the same arithmetic
operators that we have in math for
example we can add numbers we can
subtract them multiply them and so on so
let's print
10 plus 3. let me run this program we
have 13.
so this is the addition operator we also
have subtraction
we have multiplication
and division now technically we have two
different types of division operators we
have a division with one slash and
another with two slashes let's look at
the differences if you use a single slash
slash
we get a floating point number that is a
number with a decimal point but if we
use double slashes
we get
an integer a whole number we also have
the modulus operator that is indicated
by a percent sign and this returns the
remainder of the division of ten by
three so
that is one and finally we have the
exponent operator that is indicated by
two asterisks so this is 10 to the power
of three so when we run this we get a thousand
thousand
now for all these operators that you saw
we have an augmented assignment operator
let me explain what it means so let's
say we have a variable called x
and we set it to 10.
now we want to increment the value of x
by 3. so we have to write code like this x
x
equals x plus 3. when python executes
this code it's going to evaluate this
expression or this piece of code the
result of this expression is 10 plus 3
which is 13. then it will store 13 in
the x
now there is another way to achieve the
same result using less code we can type
x plus equal three
what we have on line three is exactly
identical to what we have on line two so
what we have here is called the
augmented assignment operator so we have
this assignment operator but we have
augmented or enhanced it
now here we can also use
subtraction to decrease the value of x
by 3 we can use multiplication and so on
so these are the arithmetic operators in python
all right let me ask you a question i'm
going to declare a variable called x and
set it to 10 plus 3 times 2. what do you
think is the result of this expression
this is a basic math question that
unfortunately a lot of people fail to answer
answer
the answer is 16. here's the reason in
math we have this concept called
operator precedence and that determines
the order in which these operators are
applied so multiplication and division
have a higher order so this part of the
expression gets evaluated first so 2
times 3 is 6
and then the result is added to 10. that
is why the result of this expression is
16. now in python operator precedence is
exactly like math but we can always
change it using parenthesis for example
in this expression if you want 10 plus 3
to be evaluated first we can wrap it in parenthesis
parenthesis so
so
like this now when we execute this code
we're going to see 26 because 10 plus 3
is 13 and that divided by 2 is 26. let's
verify this so print x
so you learn about the arithmetic
operators in python now in python we
have another set of operators called
comparison operators we use these
operators to compare values let me show
you so i'm going to declare a variable
called x
and set it to an expression like this 3
is greater than 2. so what we have here
this piece of code this expression is
called a boolean expression because it
produces a boolean value so in this case
because 3 is greater than 2 the result
of this expression is the boolean true
so if we print x
we get true on the terminal
so here is the greater than operator we
also have greater than or equal to we
have less than we have less than or
equal to
here is the equality operator which is
indicated by two equal signs do not
confuse this with the assignment
operator so here we're comparing three
and two for equality so if we run our program
program
we see false because 3
does not equal to 2.
so here's the equality operator we also have
have
the not equality operator that is
indicated by an exclamation mark
followed by an equal sign
so let's quickly recap
here are the comparison operators we
have in python greater than greater than
or equal to less than less than or equal to
to
equal and not equal
these operators are extremely important
in real python programs because quite
often we have to compare values to
evaluate certain conditions you're going
in python we have another set of
operators called logical operators we
use these operators to build complex
rules and conditions let me show you so
i'm going to declare a variable called
price and set it to 25.
now let's print
a boolean expression like this
price is greater than 10.
now let's say we want to check to see if
the price is between 10 and 30. this is
where we use the logical and operator so
we type and and right after that we type
another boolean expression surprise less
than 30. so with this and operator if
both these boolean expressions return
true the result of this entire
expression will be true take a look so
in this case we get true
because the price is between 10 and 30 dollars
dollars
we also have
the or operator
with the or operator if at least one of
these boolean expressions returns true
then the result of this entire
expression will be true
to demonstrate this i'm going to change
price to 5. let's see how python is
going to execute this code so first it's
going to look at this boolean expression
is price greater than 10 no it's not so
it will keep going
then it will look at the second boolean
expression is price less than 30 it sure
is so the result of this entire
expression will be true take a look
there you go
we also have the not operator which
basically inverses any values that you
give it let me show you so
we're going to have one boolean
expression price greater than 10. the
result of this expression is false
now if you apply the not operator
this will inverse false to true so when
we run the program we get true
so let's quickly recap in python we have
three logical operators we have logical
and which returns true if both
expressions return true
we have logical or which returns true if
at least one expression returns true and
we have not which inverses any value
in this tutorial we're going to talk
about if statements in python we use if
statements to make decisions in our
programs for example we can declare a
variable called temperature and
depending on the value of this variable
we can print different messages on the
terminal let me show you
so here's our temperature variable
we set it to 35.
now let's say if temperature is greater
than 30 we want to print a message
saying it's a hot day so we type if
then we type a condition and this is
where we use our comparison operators so
we type temperature
greater than 30.
then so we add a colon and see what
happens when i press enter now
the character is indented and this
represents a block of code so the code
that we write over here will be executed
if this condition is true otherwise it's
not going to be executed let me show you so
so
we're going to print
it's a hot day
and by the way note that here i've
surrounded the string with double quotes
because here we have a single quote as
an apostrophe so i couldn't declare a
string like this with single quotes if i
typed it's a hot day
look python gets confused because it
thinks this single code represents the
end of our string so it doesn't
recognize the subsequent characters okay
so that's why we use
double quotes here
so we can have an apostrophe in our string
string
so it's a hot day
now if i press enter again
the carrot is indented so the code that
right here will be part of our if block
and it will get executed if this
condition is true so here we can print
a second message drink plenty of water
now to terminate this block we press
enter and then press shift and tab
the carrot is no longer indented so the
code that we write here will always get
executed no matter what whether this
condition is true or not
now in c based programming languages
like c plus c sharp java and javascript
we present a block of code using curly
braces so
you start a block of code using a left brace
brace
and then end it using a right brace in
python we don't have curly braces so we
use indentation to represent a block of
code okay so
so
in this case
these two lines are indented and that
means they are part of this block of code
code
now let's run the program and see what happens
happens
so we see these two messages because the
temperature is greater than 30. now
now
if i change the temperature to 25
and run the program again we don't see
anything okay now
now
after this block let's print done
done
because this code is not indented it
will always get executed it's not part
of our if block okay so take a look
here's the down message now
now
let's add a second condition so if
temperature is not greater than 30 that
means it's less than or equal to 30. so
i'm gonna add a second condition so if
the temperature is between 20 and 30 i
want to print it's a nice day
so here we type l if
that is short for else if
and here we type a second condition
so temperature greater than 20.
we add a colon press enter now we have a
new block
so here we can print
it's a nice day
so if this condition is true that means
the temperature
is greater than 20 and less than or
equal to 30. now what we have here is
called a comment that is why it's grayed
out it's not real code it's just some
note that we add to our program python
is not going to execute this so whenever
we type a pound sign what we have after
is treated as a comment okay so
so
if this condition is true then we're
going to see this message on the
terminal let's run our program and
verify this
there you go the temperature is 25
that's why we see this message
now we can have as many conditions as we
want there are no limitations okay
so let's add another condition
l if
temperature is greater than 10 then
then
we're going to print
it's a bit cold
now in this case if this condition is
true that means the temperature is
greater than 10
and less than or equal to 20.
now finally if the temperature is less
than 10 let's print a message saying
it's a cold day so
so
here we type else then we add a colon
and now we have a new block
so this code will get executed if none
of the above conditions are true
it's called
so this is how we use if statements to
here's a great exercise for you to
practice what you have learned so far i
want you to write a weight converter
program like this
so this program is asking me my weight i
enter 170.
next it's asking me if the weight is in
kilograms or pounds so i can type k for
kilograms or l for pounds i can type a
lowercase l or an uppercase l it doesn't
matter so let's go with a lowercase l
now it tells me weight in kilogram is 76.5
76.5
so go ahead and spend 5 minutes on this
exercise you can use the comment box
below to share your code with others and
then when you're done come back see my solution
so first we call our input function to
ask the first question
wait we get the result and store it in a
variable called weight
next we call the input function one more
time to ask the second question
is this in kilogram or
pounds we get the result and store it in
a variable called unit
this is where we're going to use an if statement
statement so
so
we want to check to see if unit equals
equals k
k
then we should convert the weight to
pounds and print it on a terminal however
however
with this code if i type a lowercase k
this condition is not going to be true
because earlier i told you that python
is a case sensitive language so
so
we need to convert this string to
uppercase earlier we talked about string
methods so if we type dot we can see all
the functions or methods available in a
string object so we use the upper method
and this returns a new string in case
now if this condition is true first we
need to convert the weight to pounds so
we declare a new variable called converted
converted
get the weight and divide it by 0.45
and then we can print this on a terminal so
so
we say weight
in pounds is
then we append converted
now to terminate this block we press
shift and tab
else colon
so if this condition is not true that
means the weight was entered in pounds
so we need to convert it to kilograms
once again we declare a variable
converted and set it to weight times 0.45
0.45
and then we print
weight in kilograms
and here we concatenate
this string with converter all right now
we need to terminate this block so we
press enter then shift and tab good
now if we run this program we're going
to see an error let me show you so let's
run it
here i'm going to enter 170
then i type a lowercase l
okay here's an error
can't multiply sequence by non-end of
type float so this is where we got this
error when we try to multiply the weight
by 0.45 so
so
that is line seven in our code now the
reason this is happening is because the
wait variable is storing a string object
because earlier i told you the input
function always returns a string so here
we need to convert the weight
to a number we can either use the end or
the float function
let's run the program one more time so
so 170
170
in pounds
here's the second error can only
concatenate string not float to string
and that error occurred
over here
when we try to print the weight in
kilograms so
look at line seven
in this case weight as an integer we are
multiplying an integer by a float and
the result of this operation is going to
be a float
now on line eight we are trying to
concatenate or combine a string with a
float and python doesn't know how to
execute this code
to solve this problem we need to convert
this flow to a string so here we use the
built-in stir function
let's run the program and see what happens
happens so
so
170 in pounds and here's my weight in
kilograms now let's try entering a
weight in kilograms so run it one more time
time
let's say 76 kilos
kilos
here we get a familiar error can only
concatenate string to string not float
so this error occurred on line five
where we try to concatenate a string
to a float so once again we need to
convert this to a string object now
let's run the program one more time 76
76 kilos
kilos
is equal to 168 pounds
hey guys i just wanted to let you know
that i have an online coding school at
codewoodmosh.com where you can find
plenty of courses on web and mobile
development in fact i have a
comprehensive python course that teaches
you everything about python from the
basics to more advanced concepts so
after you watch this tutorial if you
want to learn more you may want to look
at my python course it comes with a 30
day money back guarantee and a
certificate of completion you can add to
your resume in case you're interested
in this tutorial we're going to talk
about while loops in python we use while
loops to repeat a block of code multiple
times for example let's say we want to
print the numbers one to five a poor way
of doing this is writing code like this
print one then print two print 3
print 4 and print 5.
now why is this a bad approach well what
if we wanted to print the numbers 1 to 1
million we don't want to write 1 million
lines of code each line printing a
number this is where we use while loops so
so
we'll start off by declaring a variable
like i and set it to our initial number
let's say one
then we type while and here we type a
condition so once again we can use our
comparison operators
let's say i less than 5 less than or
equal to 5.
as long as this condition is true then
the code that we write inside of the
while block will get executed so here we
type a colon then press enter now we
have a block of code
in this block we can print i
and then we need to increment i y one so
we set i to i plus one if you don't do
this i will always be one and this block
of code
will get executed indefinitely it will
never terminate basically our program
will continue running until it runs out
of memory so
so
in the first iteration i is 1 is less
than 5 so python is going to execute
this block of code it will print 1 on
the terminal and then i becomes 2.
then the control moves back over here so
python evaluates this condition
2 is less than or equal to 5 so the
condition is true and once again python
is going to execute this block one more
time in the second iteration we're going
to see two on the terminal and then i
will become three so this will continue
until this condition is no longer true
let me show you so
let's run this program
now we see the numbers one to five so
this is the beauty of while loops
i can easily change five
to one
thousand and by the way i'm separating
these three digits using an underscore
this makes my number more readable we
don't have to add this but it just makes
our code more readable
so let's run the program
now we see the numbers 1 to 1000. it's
much easier than 1000 lines of code each
printing a number okay now let me show
you something really cool
so i'm going to change this
to 10.
now instead of printing i i want to
print an expression so i'm going to
multiply i
by a string an asterisk
now you might be confused here because
earlier i told you that in python we
cannot concatenate a number to a string
but here i'm using the multiplication
operator well this is different we can
multiply a number by a string and this
will repeat that string based on the
value of that number so if i is one
we're gonna see one asterisk if i is
five we're going to see five asterisks
let me show you so when we run this program
program
we see this triangle shape because in
the first iteration i is one so we see
one asterisk in every iteration i is
incremented by one so we see one extra
asterisk and finally in the last
iteration i is 10 and we see 10
so you have learned about three types of
data in python we have numbers which can
be integers or floats
we have booleans and strings
these are what we refer to as primitive
or basic types in python now in python
we have a bunch of complex types as well
these complex types are very useful in
building real applications
in this tutorial we're going to talk
about lists we use lists whenever we
want to represent a list of objects like
a list of numbers or a list of names let
me show you
so i'm going to declare a variable
called names
and set it to a list of names
so here we add square brackets to
represent a list and now we can add one
or more objects inside this list in this
list we add a bunch of names like john bob
bob marsh
marsh sam
sam
and mary so we separate this element
these items using a comma okay now
now
let's print our list so print names
take a look
it comes out exactly like how we wrote it
it
now we can also get individual elements
in this list for example if we want to
get the first element in this list here
we type a pair of square brackets and
inside the square brackets we type an
index the index of the first element in
this list is zero so now when we run
this program we're going to see john on
the terminal
there you go now
now
in python we can also use a negative
index this is a feature that i
personally have not seen in other
programming languages
so if 0 represents the first element in
this list what do you think
negative 1 represents it represents the
last element in this list let's verify
it so let's run the program and here's mary
mary
what about
negative 2 well that represents the
second element
from the end of the list
so let's run the program and here's some
then we can also change an object at a
given index for example let's say here
we made a mistake and this john should
not be spelled with an h
so we need to reset it we type names of zero
zero
now we treat this like a regular
variable so we set it to a new value
we set it to john without an h now let's
print our list
and here's our updated list beautiful
we can also select a range of values for
example let's say we're only interested
in the first three names
so over here we type square brackets
and here we need to type two indexes a
start index and an end index
our start index is a zero because we
want to start from here
and our end index is going to be zero
one two plus one that's going to be
three so we add a colon three so python
is going to return all the elements from
the start index up to the end index but
excluding the end index so it's going to
return the elements at index 0 1 and 2.
take a look
here are the first three names
and by the way
this expression does not modify our
original list it returns a new list so
right after this print statement if we
print our original list
you can see that it's not changed
earlier i told you that strengths in
python are objects objects in
programming are kind of like objects in
the real world like your mobile phone
your bicycle the remote control of your
tv and so on they have certain
capabilities so if we type a string here
and then press dot we can see all the
functions or methods available in a
string object in python
now lists are also objects so they have
a bunch of methods for adding items or
removing them and so on let me show you
so i'm going to declare
a list of numbers
let's say 1 2 3 4 and 5.
now to add a new element at the end of
this list we can use the append method
so we type numbers
that append
and here we type 6.
now let's print our list
so here's our updated list beautiful
now what if you want to insert a number
somewhere in the middle or at the beginning
beginning
for that we use the insert method
so we're going to call the insert method
now on the top
go to the view menu and
and
look at parameter info look at the
shortcut on a mac computer it's command
and p
on windows it's probably control and p
if we use this shortcut we can see the
values that this method expects
so the first value that this method
expects is an index value and the type
of this value is an integer
so if i want to insert a value at the
beginning of this list i should pass 0
as the index of the first element right
so let's pass 0. now
now
the second value is highlighted so the
second value is an object and the type
of this is t that basically means this
can be any type we can pass a number we
can pass a boolean we can pass a string
we can pass a list or any type of
objects in python
so i'm going to pass negative 1. now
let's run our program
you can see negative 1 appeared at the
beginning of our list
we also have a method for removing items
so let's call remove
remove three
three
let's run the program
three is gone we only have one two four
and five
now if you wanna remove all the items in
the list we call the clear method so clear
clear
this method doesn't expect any values
so let's run our program our list is empty
empty
now sometimes you want to know if a
given item exists in our list or not to
do that we use the in operator so
let's remove this line
instead of printing our numbers list i'm
going to print an expression one
one in
in numbers
numbers
so here we're using the in operator
we're checking to see if one is in the
numbers list so this is a boolean
expression it returns a boolean value
take a look
so we get true
obviously if we search for a value that
doesn't exist in this list
like 10
we get false okay
now finally there are times you want to
know how many items you have in the list
to do that you can use the built-in lend function
function
so let's print
len of numbers so len
is a built-in function just like the
print function that is why it's
highlighted as purple it returns the
number of elements in a list take a look
when writing python programs there are
times you want to iterate over a list
and access each item individually let me
show you so i'm going to declare
a list of numbers
one two three four five
now if we print this list
it comes out exactly like how we wrote
it using the square bracket notation but
what if we wanted to print each item on
a separate line that is where we use the
for loop let me show you so we're not
going to print the entire list
instead we're going to type 4
now we declare a variable which is
called a loop variable
let's call it item
then we type in numbers
numbers
next we add a colon to start a block of
code so this is what we call a for loop
with this for loop we can iterate over
all the items in this list
in each iteration this item variable is
going to hold one value so in the first
iteration item is going to be equal to 1
and the second iteration is going to be
equal to 2 and so on so
now if we print item
and run our program
we see each item on a new line
so this is how we use a for loop now we
could also achieve the same thing using
a while loop but our code would be a
little bit longer let me show you so
we would have to start by declaring a
loop variable outside of our while loop
let's say i we set it to zero
now we say while i is less than
here we need to find out how many items
we have in this list
so we use the len function
len of
numbers as long as i is less than the
length of the list print
print
now we can use the square bracket
notation to get the element at this
index so
numbers of
i now we need to increment i by one so i
equals i plus one
let's run the program and see what we get
so we get the numbers one to five these
are coming out from our for loop and
then we get the numbers one to five one
more time these are coming out from our
while loop now if you compare these two
approaches you can definitely see that
the implementation using the for loop is
shorter and easier to understand we
don't have to use the square bracket
notation we don't have to call the len
function we don't have to declare a
variable a loop variable and then
increment it explicitly
so with the for loop in each iteration
the item variable will automatically
in this tutorial we're going to talk
about the range function in python we
use the range function to generate a
sequence of numbers let me show you so
you type range
this is a built-in function just like
the print and input functions here we
can pass a value like 5 and this will
return a range object
a range object is an object that can
store a sequence of numbers let me show
you so
let's call that numbers
so this is a range object
in this object we're going to have the
numbers 0 to 5 but excluding 5.
now if we print numbers
numbers
we're going to see this message range of
zero to five not the actual numbers
because this is the default
representation of a range object to see
the actual numbers we need to iterate
over this range object using a for loop
in the last video you learned how to
iterate over a list using a for loop but
we can also iterate over a range object
using a for loop basically we can use
the for loop with any object that
represents a sequence of objects
so instead of printing numbers
we're going to use a for loop
for number
in numbers colon
we're going to print number
number
take a look
now we see the numbers zero to four so
so
range of five
generates a sequence of numbers starting
from zero up to the number we specify here
here
now if we supply two values
the first value is going to be
considered the starting value
and the second value is going to be
considered the ending value and it's
going to be excluded so range of 5 to 10
is going to generate the numbers 5 to 9.
take a look
there you go
now we can also supply a third value and
that will be used as a step so let's say
instead of having a sequence of numbers
like five six seven eight nine we wanna
jump two numbers at a time so 5 7 9 and
so on so here we pass 2 as the step take
a look
so we get these odd numbers 5 7 and 9.
so this is the range function in python
like quite often you see the range
function used as part of a for loop
because we don't really need to store
the result in a separate variable we can
call the range function right here where
we are using the numbers variable so we
can type range of five and this will
return a range object holding the
numbers zero to four take a look
there you go
so we don't really need to store the
result in a separate variable like numbers
numbers
in this tutorial we're going to talk
about tuples in python tuples are kind
of like lists we use them to store a
sequence of objects but tuples are
immutable which means we cannot change
them once we create them let me show you
so i'm going to start by defining a list
of numbers 1 2 3.
now we use square brackets to define a list
list
and parenthesis to define a tuple so now
this numbers variable is storing a tuple
if we try
to reassign let's say the first element
we're going to get an error
topple object does not support item
assignment so this is what i meant by
tuples are immutable they're unchangeable
unchangeable also
also
if you type numbers dot
you don't see any methods like append
insert remove and so on we only have
count and index
count returns the number of occurrences
of an element for example
if we have
let's say
two threes in this tuple
and call count of three this will return 2.
2.
the other method we have here is index
and this returns the index of the first
occurrence of the given element now
now
these other methods you see here that
start with an underscore they're called
magic methods it's an advanced topic and
i've covered it in detail in my complete
python programming course if you're
interested the link is down below this video
video
so tuples are immutable we cannot change
them once we create them
now practically speaking most of the
time you would be using lists but there
are times that once you create a list of
objects you want to make sure that
somewhere in your program you or someone
else is not going to accidentally modify
that list if that's the case then you
should use a tuple
hey guys i just wanted to let you know
that i have an online coding school at
codewoodmarch.com where you can find
plenty of courses on web and mobile
development in fact i have a
comprehensive python course that teaches
you everything about python from the
basics to more advanced concepts so
after you watch this tutorial if you
want to learn more you may want to look
at my python course it comes with a 30
day money back guarantee and a
certificate of completion you can add to
your resume in case you're interested
the link is below this video hey
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