Welcome back aliens. My name is Ain

Reddi and let's talk about fast API. So

when you work with Python, you can do

multiple things with Python. You can use

Python to build consolebased

application. You can use it for GUI

building. You can use it for web

framework. You can use it for AI and of

course for different things. We got

different libraries, different

frameworks. But now we are talking about

fast API which is a web framework for

Python. And this is not the first

option. We have multiple frameworks

available for Python. We got Django,

Flask and now we got fast API. In fact,

we already have a Django series which

was created 5 to 6 years ago and now I

should have gone for Flask and then fast

API. In fact, fast API was never in the

option. I wanted to explore flask but

then I looked at fast API and thought I

thought hey that's simple uh easy to go

with and it works. And the most

important thing is it has this amazing

features which we're going to talk about

now. So let's head towards the homepage

of fast API. Now before we talk about

fast API, I want to show you the project

which we're going to build to start

with. Okay. And maybe later on we'll

update this project mode. We'll add more

features based on what fast API has to

offer. Okay. Now this is a simple page

because I wanted to explore C operation

and this is what we are going to build.

Now hold on. Using Python and using fast

API we can build the back end and you

are looking at the front end. Now the

front end is actually in react and no we

are not going to learn react in this

course. This imagine this page or this

front end is already created. Now to

make it work you have to build a backend

for it. Okay example if you talk about

this things whatever you are doing here

this data is coming from the back end.

So the database which we're going to use

is posgress but you can use whatever you

want. The back end we are going to use

Python and the framework is fast API and

the front end is in react. So we are

going to skip the React part. You will

get the code as it is the entire React

application. You just have to build a

back end and run it will work. I mean it

should work uh based on your

configuration. Now what we're trying to

build here is this is a simple inventory

application. Nothing very fancy and I

don't want to launch my own startup for

this uh simple application. Right now in

this we got a products here and which in

which you can see we got list of

products and then uh I have an option of

sorting this of course this is of react

part nothing to do with the back end but

what is there in the back end this data

is coming from the back end and you can

edit this data you can see if you click

on edit it is changing here again the

part of front end but the actual saving

or updating of data is happening in the

back end uh I can add a new product here

I can just simply say refresh okay now

this is something this is the first time

I'm looking at this bug not a bug but

then how will you go to add now okay I

should have done that before okay so

refresh the page there's something I

need to update in the front end as well

anyway the point is let's say if you if

you got this front end I want to add the

ID which is let's say five and I want to

say let's say asus laptop description

budget laptop price is let's say 999 uh

and then quantity is let's say we got 12

quantity and add and you can see it has

got added which is which is here now

This is the entire front end. You can

search for the product. Example, if you

say a laptop, it will show you the

laptops, right? Again, this is a front-

end functionality of searching. But then

uh when you search something, okay, this

is filtering. We should not be using

that. Maybe I should be doing that with

the help of ID. So if I say three, you

can say there's three. So this is

basically can be done through the back

end as well. Uh what else you can do?

You can delete the items. So this is the

back end feature. So if I click on

delete pen because I don't want cheap

products in the inventory. I'm just

kidding. Pen is very important. Uh and

you can see it is got it got deleted.

Okay, simple stuff. Now I want to show

you the back end for this. And this is

the entire code repository which I'm

going to share with you. So there's a

front end folder which you can see here

and the back end is this files. Uh not

the perfectly optimized code for the

production but we are not doing for the

production now. We are basically

learning a framework right. So this

should make sense. And now let's head

towards the homepage of fast API. And

this is it. This is fast API and they

are claiming it's a fast API framework.

It's high performance, easy to learn,

fast to code and ready for production.

Uh out of this I have tested for easy to

learn, fast to code and ready for

production. I have not tested for the

high performance. But if they are

claiming it and a lot of people are

using it, so it should be okay. Now if

you want to read documentation, you can

read it from here and that's the

homepage. You can just look at for the

documentations here. and fast API is

modern fast performance. Again, I have

not tested it, but it's very easy to

work with and you will see that when

when we do that. Okay, so very very high

performance on par with NodeJS and go.

Okay, that's what they are promising. Uh

faster code we have seen this few bugs

and

okay other thing looks good. Now this is

what fast API is promising. So fast API

is basically a web framework and we are

going to do this step by step. So the

first thing we need to do is in fact

there are some prerequisites. Uh you

need to know Python. Of course we are

not going to teach you Python in this

course. So you should know Python. You

need to basically understand how

basically a web framework works. And in

in fact I'm going to give you a glimpse

uh what happens when you communicate

from a client side or whenever you

access a particular website how it

works. But having that knowledge prior

to it will be helpful. But don't worry I

will talk about it as well. And uh

that's it. You don't you need just two

things. uh in terms of softwares to do

this you need to have Python installed

in your machine and a editor now or ID

to be specific. Now you can use uh IDE

like PyCharm for Python or you can use

VS code or any other ID which you like.

We are going to use VS code here because

for PyCharm uh it will be bulky and not

everyone will be having it and people

are getting used to VS code. So let's

use VS code in this course and maybe in

between I will show you how do we run

this in PyCharm. Okay, let's that's a

separate thing but initially we'll start

with VS code and there are certain

things which we have to install and

stuff. Yeah, initially there will be

learning curve but once you get used to

it it's very easy. Okay, cool. So that's

about the introduction for fast API.

Apart from this uh make sure whenever

you watch the upcoming videos don't just

watch the videos practice them because

practicing is very important otherwise

it's of no use. and uh go through the

documentation you know in case if I miss

something just go through the

documentation and you'll be good in fact

I wanted to add one disclaimer the UI

which you are seeing here is it's

created by AI okay so if you find any

glitch here you can blame the AI if you

love it I did it I I did those prompts

with the AI so before we start coding

with fast API let's do the most

important step without which you can't

continue and that is the setup of course

set in your machine you need to have

those things so Let's go step by step.

The first thing you have to check is

open your terminal. Now based on which

OS you're using and I mean we call

terminal everywhere now. So cmd terminal

whatever you prefer open that and check

do you have python installed. So how do

you check? It's very simple. You say

python - version and if you see a

version there that means python is

there. Now I have tested with two

different versions 3.12 and 3.13 it

works. If you have a previous version, I

would recommend you to upgrade.

Otherwise, if you have a low version,

try it out. If something is not working,

just upgrade. Okay, that's one. Next, if

you want to use the front end, see

whatever front end we saw in the

previous video, it's not compulsion that

you can run that application with that

front end. It's optional. We have

another way of accessing those pages. We

can use Postman like your rest client.

Uh we can also use insomnia. You can use

swagger. And by default, fast API gives

you docs in the format of swagger. So

you can use that but front end looks

good. You will get that satisfaction.

Yeah, you have done something. That's

the only reason we have that front end.

But in case if you want to run front

end, uh you need to make sure that you

have NodeJS installed and I have tested

with version 22. Make sure that you have

upper version than this. Uh I have not

updated my node from a long time. In

case if you don't have these two

softwares and I'm assuming you have

Python because this is the advanced part

of Python. So you should you need to

have that. I will not show you Python.

Let's get towards NodeJS and this is

this is where you can click on download

and there should be option of this. This

is the latest version you can go with

LTS version. You can also go with the

current version and that should work.

Now once you have uh these two let's see

what else we need. So you need these

two. Done. Verified. Next. Now you need

an ID. So in my machine I got VS code

and I already have VS code open in one

of the screen. Let me just drag it here.

This is how it will look like. I will

just increase the font size. And this is

where we'll be doing all the work. So

make sure that you have Python, you got

NodeJS. Again, NodeJS optional if you

don't want to use the UI. Uh then you

need VS Code or PyCharm or whatever ID

you prefer. Uh next in your VS code you

need to have Python extension installed

and again I'm assuming that you have

worked on Python before it's just that

if you have not worked on Python on VS

code uh you need to make sure that you

have this extension. So micro Python

from Microsoft okay next before we do

any more configuration in VS code now

this section or this small part is only

for those people who want to run the UI.

Now in that case instead of taking a lot

of trouble what you can do is in fact I

would recommend you to do do this. So on

GitHub you have this particular folder

called front end in the project. Okay.

So this is our project and in this we

got multiple branches. If you can see we

got product with UI, product with DB,

product put, delete and post. So this is

our first repository which we're going

to start with. Again I'm going to type

everything except the front end part.

But if you jump to the last branch with

products with UI, this is what you need

to download. Okay. Uh, of course you

will get everything. But this is where

this is important for us. Now, how do

you download? It's very simple. You can

simply click here and click on download.

Now, why I would I'm recommending

download instead of this uh cloning is

when you clone you will get the entire

project. Okay? And when you open, you

will get again you will get all these

files. When you download what will

happen is you will get everything a zip

file. Unzip it and then delete the extra

folders or the extra files here. You are

only concerned about front end. Okay?

Just keep it there. Again, when you

clone it, you can also delete all the

other files. But it is easier to

download from the file explorer or the

whatever you call these days now. What

it is called? Yeah, file explorer. So

you can delete from there. So download

it, unzip it and get this folder. This

folder is important if you want to run

the UI and I'm going to do the same

thing. So I'm just going to download

this and I should have shown the steps

you know simple. So open unzip done.

This is where you got your folder. Uh

open this. You got only one branch which

is fast API demo products with UI and

out of this you need just this one

folder. Apart from this you don't need

any any of the things. You can just

simply copy this and let's create a

folder for us. I will do that in the C

drive and let me make a new folder and I

will say fast API demo recording because

I'm I'm using it for recording. So I

will use that because after some time

after a few weeks I will look at this

project and I I will not realize why I

have created this project. So let me

just create that folder in the C drive

and put your front end there. Simple

stuff. U now once you have these steps

ready what you can do is go to your VS

code and open the folder. So C drive

fast API - demo- recording and open this

folder not the front end open the fast

API demo recording folder and yeah you

got it just say trust and you are in now

once you got this project this is where

your front end is and you can run the

front end as it is uh in fact I should

be showing that now as well so let me do

that so I will just go back here go to

your terminal

and in the terminal move to front end.

So, make sure that you're in the front

end folder. And if you have never worked

on React before, this is a React

project. Let me show you some certain

things. So, this is the main

package.json. This this is where you

handle the dependencies. You write the

script, when to run, when not to run,

how to stop, how to debug and all the

stuff. Now, to run this basically, you

can simply say npm install. Now, we're

not running it. We are installing the

dependencies. So whatever dependencies

needed for this project because see if

you open this package of JSON one of the

dependency is React itself. So React is

a library. So you have to get that. Now

once you get this uh dependencies you

have to say npm installed so that it

will download all the dependencies. And

how do you know if you have dependencies

downloaded or not? In the front end

folder you will you will see one more

folder called nodes modules. And you can

you can only see that when you have your

dependencies downloaded. So we we can't

see that now when once I click on npm

install it will download the

dependencies for you and you can see it

is doing it fast and this is the folder

I'm talking about and as you can see we

got this uh downloaded and those things

are in this node modules and now it's

time to run the node or the react

project. So I will say npm start. Now

how do you know it is start? If you come

down there's a script called start. This

is where you have to enter and this will

start the project. Okay, it says

something is already running because I

think my older project is still running.

I will just close it now. No, I don't

want to use another port. Let's do that

again. And now it should start. Okay, so

it is opening now. And this is your

project. Now it says fail to fetch is

because the back end is not working. Uh

that pop-up came and went because I've

set the timer for 5 seconds. But no

products and nothing will work. Okay,

even if you add products, it will not

work because the back end is not

connected. In fact, you you can also

check because this is what you're going

to do later. Uh you can go to console

and you can see it will say something is

blocked or the server okay server is not

server is still running on the other

project. My bad. Now let's try refresh.

Yeah, this is what I was expecting. I

was not expecting cause error. So it

says error connecting or connection

refused. There's nothing on the back

end. Cool. So let's make this work. But

what other setup we need? So let's go

back here and close this. This is the

front end part. The next thing we need

in this particular setup is the fast API

itself. So what you will do is you'll

open a new terminal here and let's

install the fast API. In fact, we need

two things. One, the fast API itself

because that's a framework we're going

to use. The second thing we need here is

a web server because we are building a

web application. REST API is also a web

application. And this web application

runs on a server. You need to you need

to get that. So if you have worked on

Java before, if you want to have a web

server there, we got Tomcat. For Node,

for React or NodeJS, we got Node itself.

Uh for PHP, we got ZAM server. So for

every particular language, we got some

servers. Here we have to get the web

server which is called UION. I know

unique name instead of unicorn that went

for uon. Good. Um so what I will do is I

will get the uicon but before that I

will in in fact whenever you want to

install some packages we use something

called pip right but we have a problem

here if I install let's say if I install

fast API here so I will say pip install

uh fast API is that simple just write a

command it will install the problem is

this will install fast API for all my

Python projects so maybe I'm working on

AI as in some other project or maybe I'm

working on uh consolebased application

in some project. The moment I say pip

install fast API, it will install fast

API globally for all the projects. We

don't want it. We want fast API only for

this project. Now how do you isolate? So

basically in different uh languages they

have different ways of doing it. In

Python normally what you do is if you

want to have some packages specific to

one project you create something called

a environment your own environment or

maybe we can call it as a virtual

environment. So here we want to create a

virtual environment. So how do we do it?

It's very simple. You say python - m and

then you specify what you want to

create. I want to create a virtual

environment. So v env that's what it's

called virtual environment. And you have

to give a name to it. You can give any

name. Maybe you can say fast api project

if you want. Uh I will simply say my

environment because I want to keep it

unique. Uh so my environment. Okay. Now

the moment you do that it will create an

environment which will take some time.

Okay. So you can see it is still not

doing anything because things are

happening behind the scene and this is

what you got. You need to get this

folder. If you don't have this folder

something is wrong with the command or

the the command here. And in this you

got all your environment set up ready.

And by default you will get these two

but we want more. So what we you will do

is you will say pip. Okay. Now you have

to activate it first. Now how do we

activate? So to activate based on what

you're using. If you're using PowerShell

or a command prompt, you need to use

different script. So this is these are

the scripts. For PowerShell, this is a

script. For command prompt, this is a

script. So for PowerShell, just copy the

path. I hope this will work. Just going

for the absolute path. Let me try. Yeah,

it worked. So instead of typing,

normally you just have to type this

much. But absolute path works. Then why

to worry? In fact, you should be copying

the relative path. Yeah, this is what I

was expecting. But no problem. We are

able to run this script and that's

important. Now, how do you know it is

successful? It has created the

environment. If you see before your

path, you should be getting this your

environment name. So, your uh

environment is activated. Now, how do

you deactivate? It's very simple. You

simply say deactivate with the right

spelling. And now you're out. So, this

is how you do it. So, if you want to get

in, activate. If you want to go out,

deactivate. Now let me show you what's

the difference of I mean what how it

helps. So if I say pip list it will show

all the packages installed this in this

machine and if you scroll down this it's

a huge list for different project we got

different libraries I just keep adding

them and now okay if I activate again

and now let's check you should be able

to see only one right but then I want

two more so the what are two more so you

have to say pip install you need to get

fast API and we need one more which is

web server which Ubicon. So you will say

not unicorn Ubicon and done. When you

say run this code, I mean run this

command not code, it will download those

things for you which will take some time

and yeah so you can see we got all the

packages here. So we have dependencies

dependencies right? So there are some

dependencies where which dependencies

are dependent on uh so it will get that

as well. In fact if you want to check

you can do that uh pay list and it will

give you everything now. So you got fast

API, you got ubicon and we are happy.

That's the setup you need

and I'm tired doing the setup here. So

these two things and fast API ubicon you

need. Then you can start with the code.

Now it's time to start coding. But again

we will not be writing a lot of code in

this particular video because we have to

also understand some theory part before

we go ahead. But we'll start with coding

and then we'll get into theory. So what

I'm going to do is we got these two

things here that perfectly works. Let me

create a Python file and let's name this

as main. py. So what exactly I'm trying

to do here? So let's say whenever a user

visits the website of of course we are

not buying any domain here but we'll run

this project in the local. Okay. And the

way you can access that is by saying

localhost colon. So instead of 3,000

let's go for 8,000. What are these

things here? Now if you are new to web

development this local host see whenever

you talk about any website or any web

application you have to deploy it

somewhere right so maybe you're

deploying on some server maybe provided

by Amazon so what you do is you deploy

your application there and it is running

on the server now if if you want to

access it you have to use the IP address

because every server will have their own

IP address and since we don't want to

remember the IP address instead of that

we use domain names right so whenever

you go put to your website like when you

go to NodeJS this is their website

domain if you go to fast this is a

website domain in the same way if you

want to access particular website you

have to provide a domain name now since

we don't have a domain I'm running on my

own machine so I can use the IP address

now since we want the IP address of the

same machine I can use local host next

in your machine you can run multiple

services multiple server services and

how how will you differentiate between

these services and that's where we can

use something called a port number.

Example, when I was running a react,

react was running on port number 30,000.

The fast API will be running on uicon

server and by default the port number

will be 8,000. So when I say enter, it

says the site cannot be reached. Why is

because our server is not running. So

what we can do is we can run the server.

But before we run the server, we need to

return something, right? So let's say

the server is running and you want to

show some output here. So when you go to

this homepage it should return let's say

welcome to the list track something like

that. Now in order to achieve that what

you can do is you can create a function

because in Python when you want to

achieve something you create a function

but again it is giving you s some

suggestions. I don't want to use the

co-pilot suggestions. So I will just

nose it for some time now and okay so

let's create a function. So I will say

defaf and the job of this particular

function is to greet the user. So I can

say greet. Okay, simple function and I'm

going to print welcome to the list go

track. Okay, simple stuff, nothing

fancy. I want to print this. Okay, now

there are two problems here and I will

tell you those problems in some time. So

I will just save this. Now question

arise, how will you run this? Now of

course you can write this is your Python

file. You can simply say python main

python space main. py and this will this

should be able to print. It's just that

we are uh running it but we are not

calling it. Okay. So we have to call the

grade function. Okay. So let's call this

and run. And you can see it is printing

on the console. But we don't want to

print on the console, right? We want to

print on the web page. Now in that case,

I don't have to call it here. It should

be called through the web page. So

whenever I refresh this page or go to

this homepage, it should call that

particular function and it should return

this welcome to the list track. So that

means we we're not supposed to print it.

We are supposed to return it to whoever

is calling it. So printing is not an

idea. Now we have to return this. Okay,

that solves one problem. And once we

save it, let's go back. Run. Uh, it will

still not work. Reason the server is not

running. Okay, even if you have the

code, the server is not running. Now,

how to run the server? Of course, you

will not be using Python because Python

is for the console based. This is where

we have to use a web server. Now, one of

the web server we have already installed

is Ubicon if you remember. So, we can

use ubicon here and we can run it. So, I

can simply say Ubicon. Then we have to

provide the file name and then we have

to specify hyphen - reload. Okay. Now

let me try to run this and let's see

what you get. Okay. It says it is trying

to will the changes in the directory

because reload means the moment you say

save it will just reload. Uh uicon

running on server this. Okay. You can

see the port the address here. Now

127.0.0 zero is your own machine and

then 8,000 is a port number but here

somewhere here it says error loading the

ASGI app which is your web server import

string main must be in a format okay so

it needs a format if you can see this is

the format it is expecting here so it's

module and attribute so we are

specifying the module here which is main

this is your module because that's what

you're creating here but something is

missing some attribute is missing Uh

okay let's go step by step. Now what is

missing is we are using a web framework

which is uh fast API and nowhere we have

mentioned that we're using fast API. So

we need to create the object of fast API

and let's say the object name is app

equal to and fast API we can simply use

fast API here and create the object for

fast API. But then this is not happy. It

says uh fast API is not defined. Okay,

why it's not defined is because it is

defined. It's just that we have to

import it. So I will say import fast

API. Um no I have to import fast API but

this will be coming from fast API

library. Yeah. So from fast API import

fast API. Okay. And then you can create

the object. So this fast API is a

library. This is your class. I hope we

can see the documentation. Yes. So you

can see this is a class. Cool. Uh and

then we can create the object. And now

since we have the object here when I run

this now so I will just I can say Ctrl C

to stop the server and come back to the

main screen. And now when I run this I

have to pass main colon app. So you have

to also mention the object name. Cool.

Now it should work. Enter the server is

running. Congratulations. We can have a

round of applause. Something is working

after a very long time. And now it is

running on the server. That's cool. So

when I go to this particular page, in

fact the same page we are doing here.

And now if I hit this again, oh okay, we

got some output. Server is running but

it says not found. Okay. So there were

two problems before. First the server

was not running. Second we were not

getting whatever we want to print. Uh

but at least one problem is solved. The

server is running but we're not able to

print. So let's solve that. And before

we understand that, let's move towards

something called REST API. See, before

we go move into REST API, we got a

client and we got a server. Now, what's

the job of a server is to give services,

right? Now, this can be a file server,

this can be a web server, this can be

some other server. Now, when you say

it's a file server, the job here is to

give files to whoever who is asking for

this file. So, let's say if there's a

client A and says, hey, I want that

file, it will go to the request goes to

the server. File server says, okay, let

me search for the file and yeah, I got

the file. This is your file. That's how

the file server works. And it uses its

own protocol to do that. There's

something called FTP or SFTP if you want

to secure it. Uh on the other hand, for

the web server, what's the job of a web

server? To give the data to the user.

Now, normally this data can be in the

format of HTML or it can be format of

JSON. Now, why HTML is because in the

real world, we all use web pages, right?

So when you go to Google, when you go to

any website like Amazon, you when you go

there, you see the Amazon page, right?

You see all the products. Now you are

able to see that beautiful pages because

of the HTML and CSS and JavaScript. Now

all these things coming to the client

side from the server. So when a client

says hey give me Amazon.com the

Amazon.com says okay these are the files

take it and view on the browser. So that

works right. But the problem is when you

create this type of application because

see one application needs multiple

things. There are multiple layers here.

User normally uses front end but the

data is stored in the database. So we

got the front end and we got database.

So there are two apart two things apart.

Now user is concerned about the data. So

of course user wants a data that is

coming from the database. So don't you

think the front end should be able to

interact with the back end directly or

with the database directly? Uh we can't

do that. First of all there are multiple

issues. one is is not secure directly

accessing the database. Second uh you

will get data in normal text we want

something good and the third problem is

to access the database we have to use

SQL if it is if it is a relational

database and that's why what you do is

in fact there are fourth problem also

sometime you don't want data directly

what you want is processed data

something you have worked on something

you have applied filter on or maybe

combining multiple things your

calculations and some data in this case

what you do is you add one component in

between which is back end. So we got a

front end, we got a datab database and

now we have the back end in between. Now

back end will be returned in any

language. It can be Python, Java,

JavaScript doesn't matter, right? So

that's a back end which we build. So the

request goes from the front end to the

back end. Then back end does the

processing of it and applying logic to

it, fetching data from database if

required and then sending the response

to the client or the front end. Now this

can be in two format. one from the back

end side. You can create those beautiful

pages and send it to the client side or

you can send the front end without the

data just the layout just the layout and

then you can populate those data later

example let's say if your internet is

off and you are so let's say on your

phone you don't have the internet you

don't have your mobile connection as

well but still when you open Instagram

you can see the layout there right what

is missing is the data you can't see the

image you can't see the text but layout

is there is because the layout is fixed.

Now what is coming from the server is

only the data. Now in which format you

will get this data? The format is JSON.

Way back we used to use XML but it is

bulky and lot of issues. Now JSON is a

perfect format where you can get the

data in a structure format and it will

be less bulky to understand and you will

see some JSON data if you have not seen

that before. So this is the

communication. Now we started with rest

and now it's time to talk about rest.

Now when you send this data the data has

to be in a proper format and that's

where we got this term called rest which

is representational state transfer. See

whenever a client sends a request for

the data you are sending the state.

State means current data or current

state of the data. So you're sending the

state from the server side to the client

side or vice versa. You're sending from

data from client side to server side. So

you're sending a state. Next you need to

send the state in a representational

format. it should be easy to represent

and you are transferring it and that's

why we got this term which is

representational state transfer rest so

in order for a client to reach to the

server of course server simply not

accept all the request uh what if you

are building a website for the

e-commerce and this and the client says

hey I want to look for job here the

server can't do that now because server

says okay I was good with uh products

but now you're asking for a job I can't

do that so as a server it has to open

some endpoints. Okay, these are the

endpoints. You you can you can b browse

the products, you can buy the product,

you can do the payments. So those are

the endpoints which we have and to build

this endpoints we we use something

called APIs which is application

programming interface. So in order to

access the server we have to access

their APIs. So if you're a server and if

you want client to access you you have

to build those APIs.

Okay. So if you want this server or if

you want this client to get the data

from you by the way this is JSON okay so

if you want your client to get data uh

from the server so client has to request

and the server has to accept it now

question arise how will you accept it

now if you go towards something called

CRUD which is create read update and

delete these are the CRUD operations

right now for this operations we got

this amazing protocol for the website

which is HTTP or web applications. So

whenever we use internet we always use

HTTP. So if you check here not here

let's say if you go to this page HTTP

yes there's also S there for security

but the general protocol is HTTP. Now

HTTP HTTP says I will give you certain

methods to work with. Now this methods

will help you for the operations. So you

got get for reading, you got post for

create, you got put for update and you

got delete for delete. In fact, there

are more methods which we can use but

these are standard uh I mean mostly

used. Okay. Now after all this theory

let's come back here and let's say

greet. Now whenever send someone is

sending the request to the server we

have to understand that for the homepage

I want to return this and to do that we

have to use decorators and we have to

say app dot. Now this will have because

app is fast API itself. It has something

called methods. Now there are multiple

methods here. Uh we can use get we can

use post somewhere here there should be

post put patch uh there should be delete

as well somewhere up yeah delete so we

got all these methods I'm going to use

get here because we are getting data so

whenever you want to read something from

the server we say get and we have to

also specify the root the path okay so

I'm accessing the homepage here so if

you see I'm trying to access the

homepage and to do that I can say slash

again what are the other options we'll

see later but we I have this option here

which is slash and I think it should

work now. So if you do this the moment

you save you can see it is reloading the

server. That's what we wanted. Go back

to the homepage and refresh. You got it.

You can see that it says welcome to the

list track. And finally after talking so

long we are able to get something on the

screen. And the code is so simple right?

I mean look at the things which we have

done. Just do the setup once you get all

the libraries and this much of code and

your server is up and running with

welcome to the code track. So this is

fine where you are requesting for the

homepage and you are written a text. But

then if you remember we started with a

application where we want to work with

the products. A product will have an ID.

It will have a name uh description the

price the quantity. Now how we are going

to do that? Of course, I can just change

this URL. So, instead of having

homepage, I can say uh slash products.

Now, that's how you do it for the rest

API. Now, whenever you visit a page,

let's say if you go to Google and if you

search for Teresco, of course, you will

get all these details here. But look at

the address bar. So, it is google.com/

because that's the homepage. Then slash

search because now we have a different

path, right? So, we are searching and

then we are passing a query. So you put

a question mark and then you say the the

variable Q equal to the list. So this is

what we are searching right. Ignore the

other parts. This is just for the other

things. So we can just ignore this. This

is the important stuff. So search that's

the path and then question mark Q equal

to list. Now this is how you basically

do the query. Now when you visit a page

and if you want to pass the query as

well, this is the obvious way. But then

if you want to search something as a

resource because all the products online

or in the database in the back end they

are the resources. So you are requesting

for a resource. So instead of saying uh

question mark q there should be a

different way uh something like this. So

let's say if I want to search about

products and I will go with the

google.com this will not work but I just

want to show you how it works how it

looks basically. So it is

google.com/proucts.

Now it will it should give me all the

products from the database. Okay that's

my expectation. Then if you want a

specific product, let's say if you want

a product ID with one, product ID with

two, then you will say slash one, this

will give me the first product, this

will give me second product and then so

on. What if you want to uh add a new

product? Now this is where the things

will change. Now if you want to add a

product, how will you do it? So will you

say add here? Now that is not how you do

it. So basically what we what happens is

for the fetching you know when you want

to read you will use the same link and

for posting as well when you want to add

a new product you will use the same URL

and now you will say okay how will a

browser differentiate between when when

I want to fetch data and when I want to

save data and this is where the HTTP

methods comes into picture which we have

talked about before. So when you want to

fetch data that's when we are going to

use get. So the same URL or the same URI

but the method will be get. If you want

to submit something if you want to post

you will be using the same URL but

different method name. Okay remember

that point because we are going to do

that in this particular project. So now

I want to fetch the products right now

before you even fetch the products you

need to have the products. Now how we

are going to do that? uh since it's

already opened here. So the libraries

are already opened. I don't want to uh

open again. So if you see we have also

added pye now we have not added manually

when you ask for uh uicon you got this

by default and this is what we are going

to use now. Cool. So what it basically

does so pilent is basically for data

validation. Okay. And also if you want

to convert your data from the server

side into JSON format to send it to the

client we are going to use this. Again

this will make much more sense once we

do the coding for it. The first thing

we're going to do here is now since I

want to work with the products, what I

will do is I will just go back here and

say app dot uh again a get request but

this time instead of saying slash okay I

have to snooze my copilot and then here

it will be products because that's what

I'm asking for and I want to say get

okay and I'm expecting all the products

not just one product and here I can

define a function and all these

functions are by default async so you

don't have to mention async and then I

will say get all products

If you can be better with the uh name of

the methods, it will be helpful to read.

And then this is where you will return

the products. At this point, I'm just

going to return all products just to see

if things are working out or not. So I

will just save this. So when you save it

should reload and then let's go back

here and instead of hitting the homepage

and I'm just hitting the home page just

to check if everything is working. I

will say products enter. And you can see

it says all products. Awesome, right?

But then we don't want text as all

products. We want the actual products

and not from the database because we

have not done the setup for the database

yet. So we'll do that later. So let's

say we we have a inmemory list. We want

to work with it. So there should be a

list somewhere here. And let me just

create in fact you know we are done with

this. I can remove this or maybe just

keep it there. Why not? Uh let's me let

me just create a list here somewhere

here.

But then how will I create the list of

products because of course this is a

list of products but then we don't have

a products there. There are different

ways of doing it. Of course I can just

create uh a dictionary here by

specifying all the values. That's one

way of doing it. Otherwise if you go

with the object oriented way which is a

better way here. What I can do is I can

create a models or maybe I I can create

a product file but models make sense

because these things are called models

which holds data or which is used to

represent any data. So example if you

want to represent all the users of a

system. So that's one model. So you can

create a user model and this will

represent the users because a model will

have a name and it will have some

properties. Example here let me create a

class and this will be product and this

will have some attributes. So I will say

id of type int. Then we can have name of

type

strr. Then I can have also have a

description here of type str. Then we

can have a type of price which can be

float. And then last thing we need is

quantity of type int. Okay. So these are

the things you need. So basically you

can represent the data in this format.

So you can create one product which will

have all these properties, right? And

then you can just go back here and

create those objects, right? So I can

use the constructor of it. I can say

product. But then to use the

constructor, I don't have it here and I

can just ask for the constructor. So

this is the constructor. I hope this

will work. I have not tried this before

for this application because we were

using Pentech. But let me try. So I will

say ID is equal to one or maybe I can

just pass the value name. I will say

phone. Okay, it says product is not

defined. Uh what I will do is I will

just import this. So from models import

uh product. Okay, now there's no issue

and I can add description. So name is

int is done. I mean the ID is done. Uh

name is done. description I'll say

budget phone and then let's say the

price is $99 and the quantity let's

let's say we have 10 of it so at this

point I just have one product or maybe I

can add one more just by giving a comma

here so two laptop gaming laptop 9 and

let's say we got six quantity of this so

we got this two products and now instead

of returning all the products here I can

return the products itself right so what

it will do now is when you request for

the products it should return this list

and let's see if this works okay I'm not

sure let me try I will say enter oh we

got it so I can just repetitify this and

you can see we got the data in this

format so this thing works so basically

we can just create this thing and you

can return it from here now this is one

way right and this is working nothing

wrong with it the problem is in future

maybe you want to do data validation so

let's Say when you are send this when

you want to send this from the client

side to the server maybe maybe a client

want to add a new product and when you

say you want to pass the ID the client

is sending an ID let's say 10 that works

what if the client sends the ID as minus

one or minus 10 that doesn't that an

issue and this will accept it right this

will not say any problem there because

it's an integer uh what if you pass a

price which is negative of course price

should not be negative what if you pass

the description of only one character uh

that doesn't make sense why description

will be of one character there should be

at least two words even if you're lazy

okay so how do you do that validation

and that's where we got this particular

library called pyntic which will help

you for the data validation so we have

already seen that now how do you make

this as a pyntic so it's very simple you

come back in the models and here you can

just import you can say from py tech

because that's what you want to use we

just need one thing from that which is a

base model so I can say import base

model of course you can take it lot of

things from there so you can import all

these things from it and we are going to

use some of them later like field but

here okay why I'm deleting that part I

will just import parentic import uh base

model this is what you need and then you

basically inherit because if you want to

achieve that feature you will simply do

inheritance and you got it you got your

base model now you don't even need to

create this constructor by yourself that

is done taken care of and things you

need to change is instead of specifying

this syntax it should be with the

variables because that makes much more

sense right why do you pass in this

format so ID equal to and then the list

goes on now instead of typing in fact

this should be name so instead of typing

all the things I I just I do have the

data ready with me I'll just copy paste

that oh wait instead of saying copy

paste I should say code reuse so paste

and We got it. So you can see we got

ids. We got four ids because we got four

products. And then we got phone, laptop,

pen, table which is a name. And then we

got description. We got the price and we

got the quantity. Now with this changes,

let me just go back here and refresh.

You should be able to see all this. Now

if you're not able to see in this

format, you just have to uh download

this extension called pretty print from

the chrome and you will see in the

proper format. Now this is one way.

Okay. But what if you don't want to use

here you want some good UI to test it

out? Uh you can use something called

swagger. Now in other frameworks

basically you have to add a swagger.

With fast API you get this by default.

So what you do is you use the same URL

but not products. Remove that. You say

localhost colon 8000 and then you say

slash docs enter and you got your docs.

This is swagger. Okay. And now if you

click on greet because we have created

two endpoints if you remember we got the

endpoint if you go back to main we got

this endpoint which is for the homepage

and we got the endpoint which is /

products and here we got the first now

how do you use it if you're not if you

are using this for the first time click

here uh there will be an option of try

it out click here and then there will be

option of execute but before executing

make sure that if it is asking for any

parameter or not at in this at this

point we don't have any parameters you

can click execute And this will respond

here. So it says welcome to the disco

track.

Uh scroll down. We got another one which

is all products. Expand this. Scroll.

And you can say try it out. Execute. And

it will give you all the products here.

Right? Also it returns if you observe it

returns a code 200. Again we have not

talked about that here but we'll see.

Remember this point the code 200. uh

just to give you a hint there are

multiple codes available if something

goes wrong on the uh with these

resources uh or the file is not found or

something you will get 404 you might

have seen that everywhere right so

that's a part of the status code okay so

this is how you basically fetch all the

data now it's time to fetch one product

because now we are getting all we don't

want it let's say if I pass an ID one we

want that in this case how will you do

it should be simple right let me create

a new function and this time I will say

get product by ID. Okay, so it should

accept an ID and based on that it will

it should return the product. Now at

this point I'm just going to pass a

variable here. Let's say ID and this

will be of type int. This is the

variable I'm going to work with and

based on the ID should return and of

course there should be a mapping as

well. So let's say at app.get get and

then you have to specify the URL and of

course that should be product or maybe

you can say products but let's say

product slash

u now so let's say if you simply say

product and by default I'm assuming the

ID is one how will you do it so one of

the easy ways if you know that the ID

will be always in sequence and there's

no missing point uh you can simply say

uh you can use the feature of list where

you can fetch a particular element based

on the ID something like this. I can say

return

uh product and then I can specify let's

say if I'm assuming that's a first

element I can simply return by zero.

That should work right and let's say we

are not even using that. So we can

remove this till this point and at this

point and let's work with it. And now

let me hit this URL product not from the

swagger but from here localhost col

8000/

product not products product enter and

this is returning the first product.

Okay, that's cool. But every time it

will return the first product. And the

second problem is what if you want to

fetch the product ID two and two itself

is a first product. Then this will work.

And this will not work. That means uh

because it will always return zero. And

even if you say one, what's the

guarantee that the second product has

the ID two? No guarantee, right? Even if

you want to fetch the ID with two, in

that case you have to pass two. Okay? So

what you will do is you will map it with

two so that you will get two and now I

can just say one because that's that is

two okay now that's a problem right I

got two here and I want to use that two

here how will I use this two here that's

that's crazy now we can what we can do

is we can hardcode so for two it should

return uh with ID two we can do some

coding for that and for three we should

do do some coding for that and for four

we should do some coding for that uh

what if you have 100 products you have

to get 100 methods. That means we have

to make this two dynamic. In this case,

if you want to make it dynamic, just put

it in curly brackets and use a variable

name. Let's say ID. So you can say

product / ID. But don't mention ID.

Mention the number and that number will

come here because this is a dynamic path

and you can use that path here. So you

can say ID type int. So whatever name

you are going to use here, use the same

name and you are okay. And now I can use

this ID. So I can simply say id minus

one. That should work right. Let's try.

So go back here and now product slash.

If you say one, you will get the first

product. If you say two, you got the

second product. And I will also do p5

here. And if I say four, you will get

fourth product. But if you say six, it

will say internal server error. And

there will be error here as well. So

because we are going out of list. Okay.

Okay. And that's why you have to handle

the exceptions. But I'm not going to do

that. I'm just want to make it simple.

Uh this is working. But then the problem

is what if you don't have a product like

this. Maybe you have product five and

six here. But still this will not work.

So even if you say six enter, it will

say internal sub error because here we

are sending the request 6 - 1 which is

five and we don't have the sixth

element. Okay, this is not the right

logic. So let me just write the right

let me just write the correct logic

here. So we have to search the products

for the ID. So I'm just going to iterate

product in products and then here I'll

check if the ID provided by the product

or one of the product. If that ID

matches with this ID in that case return

the product. If it is matching return

the product otherwise you can return

product not found.

Okay. Uh that should work. But there is

an error here. There should be double

equal to no problem. Now cool. Let me go

back here. And now let's fetch for six.

It is working. Perfect. If you search

for four, there's no product as four. So

it says product not found. Just to

verify there's no ID four here. Okay.

And what if you want to do it for two?

It is working. So this is how you fetch

a single product. Okay. That's the

logic. Okay. So that's for fetching all

the records, one record. But now what if

you want to add a record? So maybe we

have four. or I want to add more. In

that case what you will do is uh let's

create a function and this will be add

product and now you can guess I don't

have to tell you now uh you guessed it

right we have to say app dot now we

can't use get because we are submitting

data we are creating a resource in that

case you have to say post and then the

URL the URL will be same as previous

which is product we don't have to modify

that how will you differentiate between

a single product or this this slash and

this one is because of the get and post.

Now how will you add a product? So we

have a in my list here. I can simply say

the products in this I want to add. So

product dot we have a method called

append list. We can use that and we can

append it with oh we can append it with

what we are sending data from there. We

have to also accept that data here. Now

in which format you will get the data?

You will get the data in the format of

product itself. So you will get the

product of type product. So just get

that and add it here. Okay. So what

we're doing here is we are creating a

method called add a product of type

post. So you can see we have we have

this we have this URL which is product

and then from the client side you have

to send the product details that will go

here and then you are appending. But the

question is how will you send this data?

Okay. So let me just save this. So now

we have to also return say return

product whatever we are getting just

return that. Okay. But how will you make

this work? This is this should be a bit

tricky. Let's try. First of all, we

can't do that from the browser directly.

We need a react application or I can use

swagger because for post you need a

form. Okay, we don't have a form here.

But swagger says don't worry, I will

take care of it. Just refresh the

swagger. Now I don't want to greet. I

just want all the products. I will just

keep it open. Uh and I will keep open

the ad product. Okay. In fact, we have

Okay, let's just test add product. And

if you expand add a product, it will

give you some details. The of course you

can click on try it out. But it will

give you a schema. Okay, default schema

where you can add the elements or add

the values. And let's see. So I will

just click on try it out. And you can

edit this values now. So let's say this

is eight. And I'm going to add a new

product. Let's say watch

from I will say Titan watch. And the

price is let's say $80. And the quantity

we have is let's say 50 because we have

it. Okay. So this is the data which you

have to add and this has to be in a JSON

format. So when you click on execute

this data goes to the server and you can

see this is the request it is sending

using curl behind the scene and the URL.

Okay. So there is some problem. It is

sending request for product. Oh I forgot

to add a slash here. One slash and this

is what happens. Okay. Uh let me just

copy this so I don't I don't have to

type it again. Uh execute. So do I need

to refresh this add product.

We'll say try it out. Paste. Execute.

And yeah, this time it worked. You can

see there's no error. This is the URL

and you got the data here and this is

200. But how do we check if this get got

added to the list? Let's go up. Let's

see all the products. Try it out.

Execute. This is what we have done

hardcoded. And this is the new data.

Okay, things are working out. So this is

how you fetch all the record. This is

how you fetch one record. And this is

how you work with uh posting the new

record. Oh, this is working. And now

it's time to focus on put and delete. So

basically, if you want to update the

product or you want to delete a product,

how will you do it? So that's what we're

going to see now. Now before I do that I

just want to remove this extra spaces

from here and let's look at the code. So

basically we got this main. py where we

got all the product in the list. We are

still not working with database and we

basically have this methods like get and

post. Now in this get we are fetching

all the products and in this get we are

fetching a product by its id and then

here we are basically adding a new

product. Okay. Uh so now let's try to

update it. But before we do that, in

fact, there are a lot of things which

have to do before we do that because if

you can see my shirt color has changed.

It's a new day and I have to do that

steps once again to run this. So, first

of all, I will run this server. Before

that, I have to change my environment.

So, the virtual environment it is using

now. Oh, it is creating a new

environment. No, no, don't create a new

environment. I'm using a wrong thing. I

I I have to activate it. So, activation

done. And now it's time to run this. And

also I will disable my co-pilot or

snooze it for some time. And let's run

this. And this will load the server. No

problem with the server loading. And we

have to also run the front end. Make

sure that you don't run this in the

environment. So you have to deactivate

this so that you will come out of the

environment. And now you can run the

front end. And you have to switch to

front end and say npm start. Now the

front end started as well. Uh but again

we the front end is not fully configured

yet and that's why you can see it is

failed to fetch. So there's no need to

run the front end. I don't know why I

run that muscle memory maybe. Uh but let

me just go with this. So there's a

problem with the front end. That's fine.

Okay. But but the back end is running

and the way you can test it you can just

go to localhost col 88 uh 8,000 and then

slash here we have to say docs which

will load your uh swagger in which you

can test all the things and we need to

first test it out if it is working so

that we can continue. So it's still

working nothing is wrong yet.

Okay so let's go back here and now it's

time for the update. Now if you want to

update a product how will you do it?

First of all, you need a function. And

we'll name this as a update product

function. And then this will uh also

accept the product itself. But then with

product, we have to also pass the ID. So

which particular product you want to

update, right? So you can ask for the

ID. So I will say ID of type int. And

then you will also ask for the product

because that's what you're going to

update. Now if you want to update a

particular field of a product, you can

also use patch. But we'll not be doing

that here. We'll be only using put and

this is where you will update and we

also do the mapping for this. This

should be app dot now instead of using

get or post we are going to use put and

here we'll say the same URL which is

product. Cool right and now I can

basically write the logic for updating

our product. So it says there's an error

on line number 36 and there is an error.

So you can see it is expecting a block

but I'm going to write a code for

updating. Now when you want to update

you want to update the product from the

products list with this particular

product right and uh which one to update

now you have to basically iterate

between these products to find which ID

it is matching with 1 2 or five and six

and then you can do it. So in that case

I can say use a for loop. I'm going to

start with I uh in range or maybe I can

also use product but then I can't

replace it. So let's go with the range

itself because I want the uh index of

it. So I will say uh for i in range and

I will go till the last value and for

that I have to say I mean second last

value. So length of products. Now once

you have this range it will start from

zero. It will end at three because we

only got four products here. Right? And

of course in future if you add new

products this will go to the second

largest value. So if the value if the

length is 10 it will go till 9. Okay

then you will basically check for each

product. So you can check products of

zero or sorry products of i and then you

can check the ID if it is matching.

Okay, if it is matching that means I

have to use if. If it is matching with

the ID whatever you have passed in that

case for that location that means

products of I for that location replace

it with the product which you got from

the client. Looks good. And if this is

successful you will return product added

successfully. Again this should be a

JSON data but I'm sending a plain text

but that's fine. It it works. And what

if you don't find any products? Of

course, this will come out from there

and then you will say return no product

found or you can say product not found

whatever works. So this is the update

code and I want to verify if this is

working. So the moment I saved it this

got reloaded. I can go back to swagger

now or the docs refresh this and first

of all let's get all the products from

here and we'll update one of it. So

execute and you got all the products.

Let's say I want to update uh this table

here. So I will just copy this and the

ID is six. Remember that go back to put

because this is what you want to do

update product and you will update. So

you will say try it out type here six

and replace this schema with your

schema. In fact you can uh change the

values from here but I will just paste

it. Then I will keep the idea same. I

will change it to table desk and I

wouldn't table for your computer. Okay.

And then price since we have added this

description the price should go up.

That's what we do, right? And let's say

the quantity remains 20. Okay. So we

have changed name price description but

not ID and quantity. Let me execute.

Let's see what goes wrong. Nothing went

wrong here. Uh it says product added

successfully. That's great. That means

if you go back now here and if you try

to

execute this once again and look at the

product. So we got table test changed uh

description changed price change. Okay,

that's how update works. But now let's

work with delete. So let's go back here

and now you help me. It's okay. Now the

question is how will you help me when

you're watching this video? Think just

think about it. What will be the logic?

I will get it. telemetry

uh so I will say app dot it should be

delete the method okay and then you have

to also pass the URI we'll go with the

same URI and as I mentioned before all

these URIs are same what is changing is

the method here okay so let's define a

method so we'll say define delete or def

delete product okay now question arise

based on what value you want to delete

maybe a user will send the entire

product and then you can delete it or uh

id is enough right because every product

will be different based on its id so you

can simply pass an id here let's do that

so except the id so we'll say id colon

int and based on the id you will delete

it but again you have to iterate right

because you have to match with ID it's

matching with so we'll say for in fact

the same code which we have written

before for range and this will be length

of products and then you can check if

products

of I. In fact, you have to match the ID.

If it is matching with the ID which you

mentioned from the client side, in that

case delete

the products of I. As simple as that.

And if this works, you can return

product deleted. And what if you don't

find the product? So you have to some

mention that somewhere. So we say return

same thing product not found. So once we

are writing no product product found and

once we are we're writing uh product not

found. Uh there should be some

consistency right and I'm not doing it.

Okay. So we got this products here right

now I want to delete let's say uh six

itself or maybe in between let's say I

delete the second one two. So the ID is

two. Let's go back to

uh okay I think we have to reload this

put and delete. Delete is here. And we

are going to delete two. So I will just

type two here and execute. Nothing much.

And it says product deleted. That's

great. Let's go back to get all

products. Try it out. Execute. And here

we go. You can see we don't have to

anymore. And that's how you update and

delete. But I want to show you the code

once again. And this is it. So this is

update product where you are getting the

id getting the product the new details

which you want to add and then you are

iterating and then you are basically

checking for each id if it is matching

or not. The moment you find the match

you will update the product from the

list and that's how you update for

delete. Same code it's just that instead

of updating we are deleting it. Cool

right? Uh but then remember everything

what we have done now we are doing with

inmemory list. So this is a list but in

the real world we don't use list right

we use a permanent storage maybe like

posgress or MySQL or any type of

database it can be RDBMS it can be nosql

databases or somewhere and now it's time

to save the data in the database so

whatever option we were doing like

creating updating uh deleting and

reading this should be done through the

database now database you can use

anything which you want maybe a CSV file

you can use uh NoSQL databases or you

can use RD DBMS and here we are going to

use the R DBMS. Now you have multiple

options to work with. You can use MySQL,

you can use Postgress, you can use

Oracle, whatever you prefer. Now I'm

going to use Postgress but because it's

one of the best advanced open-source uh

tool that's what they say. So if you go

to Postgress, this is what they say the

world most advanced opensource

relational database. But of course there

are other options as well. Whichever you

prefer will work. Now question arise how

will we are going to do this? Now

whenever you work with fast API one of

the recommended way is to go with SQL

alchemy. But why we need to use SQL

alchemy here. Now SQL alchemy is your

Python SQL toolkit. That's good. The

other options as well. But it also

provides you something called a object

relational mapper. Now why this is

important? See if you go back to our

code which we have done. We basically

have a class right? A class like this

where you have a product and then you

got certain fields there. Now let's say

if you want to create a database and if

you want to create a table. Now if I ask

you hey you got this particular class

here and I want you to create a table

for it. Now in your mind actually you

can do the mapping right? You can say

okay I got a class which is product. Let

me create a table called product. I got

this fields like ID, name, description,

price, quantity. I can create the table

with those columns like ID, name,

description, price and quantity. As

simple as that, right? So, and then you

got the table name, you got column

names, but you also got the column type

because in the class also when you

define those properties, you mentioned,

hey, that's an ID which is integer. So,

here also we can say integer. Now, based

on what DBMS you're working with, uh the

name will change from numbers to

integer. So, here we can have string or

wcad or text and list goes on. So, the

type defined in the class will be

defined for the table as well. But you

will say okay mapping is done but what

about the data? What about the row data?

So each row will represents one object.

So let's say we have created four

products right that was in the list. Now

each product here is the object of a

product class. Now that object goes to

database and becomes a row. So what we

are trying to do here is we are trying

to connect the object and the relations

which is tables and we are doing a

mapping for it and that's what we call

or RM. Now you will say what's the

benefit of it? You know this looks fancy

but why do we use it? See when you work

with databases like let's say posgress

or MySQL and if you have a language like

Python and whenever you want to save

data basically what you will do is you

will take the object and this object

will have the values. Now you will write

the SQL query. So let's say if you want

to create a new record in the database.

So you will write the SQL query which is

insert. So you will say insert into

product. Then you will say values and in

bracket you will mention the values.

Right? Now from where you will get this

values from the object then manually you

have to pick up the value from the

object put it there. Pick up the value

put it there. So you have to create that

query as a developer. So that's for the

insert. What about let's say if you want

to fetch then you will write the query

which is select star or based on what

columns you want to fetch based on how

many rows you want to fetch you will

write the query in that format what if

you want to update for everything you

got queries and you have to write those

queries now you will say okay I know how

to work with queries but the question is

do you want to really write that in the

python code what if someone else can do

it for you so they will say let me give

you a tool use this and let me take care

of creating all the queries for you. You

just say if you want to insert, you just

say add. If you just want if you want to

fetch maybe you can say get whatever

method is. So basically you can use

those methods or functions and this will

do the things for you. Cool, right? And

that's why we are going to use SQL

alchemy. Then the question is how do you

get this in your project? Now if you

head back to your project here, okay,

let me stop the server because we are

going to make some changes. Now if I

check pip list, nowhere you will find

SQL alchemy. You will get pyic by

default but nowhere we got SQL alchemy

right. We need to get that. Apart from

it we also need to get the driver for

posgris. Now based on what DBMS you're

working with. So if you're working with

MySQL you need a MySQL driver. If you're

working with posgris you need a postgris

driver. And we need those two things in

this project. SQL Alchemy and the driver

for Postgress. So let's install it. So I

will say pip install. So we need SQL

Alchemy and we also need the driver

which is psy cop G2. I don't know why

they went for this weird name uh because

this is PG makes sense posgress and uh

psycho. If anyone knows this let me know

in the comments. I've not not explored

why they have this weird name. uh 4C for

MySQL it's a very simple MySQL connector

for Python perfectly makes sense right

but I don't know why they went for this

name but this is a driver for posgress

and this is your SQL alchemy and you

have to also make sure and before you

work with posgris you have to also make

sure that you have posgris in your

machine if you don't have it click on

download it will download the postgris

for you based on which OS you're working

with I'm using windows and these are the

version I think in my machine I got 17

or 16 doesn't matter because the last

update was in 2022. So that is 17.6.

Uh they are releasing the beta 18 beta

is released. That's great. Uh if you

want to use beta, you can try it out.

But if you're new to the development

world, stick to the stable versions

because if something goes wrong, you

will always blame the system because

it's in beta. Maybe it's your mistake.

Now when once you get experience, once

you have worked on multiple project and

if you if something goes wrong, you can

still blame it. But at least you will

know are you really responsible for it

anyway. So you will get this download.

Now make sure that when you get this you

also get PG admin. Now if you don't have

PG admin in your machine uh or if you

don't get this by default search for PG

admin somewhere and you should be able

to get it. I think you will get that by

default. PG admin. There should be a

tick mark. Now how the PG admin looks

like. So this is how the PG admin I'm

just opening it now looks like bit heavy

to start with in fact earlier PG admin 3

was very heavy four they have changed

the interface to make it lightweight but

since it's connected with the posgress

service which is running behind the

scene uh it takes time so by time it is

opening let me just go back to our code

and let's install this so this should

take some time now since I already had

this in my system it will be faster

Yeah, it it was fast. And now if I check

PIP list, there should be SQL alchemy

and there should be the driver. Perfect.

Now once you got these two things, we

can get started and work with the

database. Okay, but I I also want to

show you the PG admin. This is how it

looks like. Uh I should zoom it a bit.

Okay. So this is PG admin and by default

I think you have to add the server by

specifying the username password.

Username by default will be posgrisis.

The password you have to set when you're

installing it. And I forgot what is my

password for this particular pg admin.

But we'll figure it out because I use

different machines for uh project and

for recording and I always mess up the

names. Okay. So we'll use this. We'll

try to save our data in the postgris

database and if you're using MySQL the

only thing you have to change is uh in

fact you have to change two things one

is a driver and second some lines in the

database connection that's it and it

will work now once we have our libraries

ready so we got SQL alchemy and we also

got the postgris driver it's time to

start with the configuration now why do

we need configuration so let's say if I

go back to main now this is where we are

and let's say if I Now say in this get

all products instead of returning this

particular list which we are doing here

I want to connect to database. So of

course before we do this there should be

some database connection. So I will

write some statements here. Okay again I

have to disable or snooze my copilot.

Okay I will write in a comment. I need

uh database connection because without

database connection how will you connect

to database? And once you are connected

then you want to fire some query right

uh which will do. So here we have to

write some query. So first we have to

create database connection and then we

can write the query. Now we know that in

fact in the previous video we have

talked about we are going to use SQL

alchemy. So I want to create this

database connection which talks to the

SQL alchemy. And to do that of course I

can do all the configuration in this

file but it's better to have in a

separate file. And this I will say

database py or you can say config. py

whatever works for you. So I will say

database. py. And this is where you have

to do do the configuration. So basically

what you need the first thing you need

here is something called session local.

Now using the session local we have to

first of all create this object here so

that we can use that object in our main

file. So database connection. So we'll

be using session local to access the

data database. But how do you create

object of session local? Now first of

all what is session? So every time you

connect to something it's a session. So

if you connect to a server that's one

session. If you connect to a database

that's one session. Okay. And you you

need to create a session before you do

this operations. Now to create a session

we got something called a session maker.

So you'll be using that and this will

create the object of session local. But

then from where you are going to get

this session maker also uh for session

local you can name it anything. If you

want to use it as only session that

works uh this is just a variable. Now to

get the session maker you need to import

that from SQL alchemy and that too from

SQL alchemy because we are going to use

ORM here and I'm going to import session

maker. Okay, this is an inbuilt part. We

just have to use it. So you can see

session maker is a class and we just

have to call the constructor. It will

create the object for us. But then this

session maker will take some parameters.

The first parameter it will take is the

for the commit. So whenever you do

database transactions normally we have

to do the commit for it. But by default

it will be auto commit. We have to

disable it. So we'll say auto commit

equal to false. And you can get these

values uh from the session maker. So if

you scroll down there should be this

variables which you have to assign. Okay

there's one constructor which is engine

we'll be passing that as well and there

should be another constructor which will

take all these values. So we can see we

have something called auto flush and

there should be something with the

commit. We'll do auto flush as well but

I'm looking for the commit. Where is it?

I should have searched for it. But

sometimes trolling works because you

come across certain new things. uh but

still I will now search for auto commit.

Yeah. So this is auto commit and I think

by default is false. So that's we can we

don't have to set that auto flush is

true. So we have to disable this but

we'll disable both. Okay. So we'll come

back here and this is false and we'll

also do auto flush as false not true.

And then the third part is you have to

set the engine. Now remember remember

when we looked at that there is also

engine which you have to set the value

for. And we can do that with the help of

bind. Bind equal to engine. Now what is

this engine here? Now engine here helps

you to connect with the database because

you have to also specify the which

database you're working with because

nowhere we have mentioned that. Now so

for your Python application yes you're

connecting with the database but which

one we have no idea. It can be MySQL,

Postgress, Oracle. So you have to

mention that also for the particular

DBMS you have to also set the username

and password. So we can do that with the

help of engine. So you can say create

engine and this is where you have to

pass all the values. So in this you have

to pass which DBMS you're working with,

what is the link to connect to it,

username and password and what is your

database name and we can put that here

and the ideal way of doing that is

something called a DB URL. So I will

create a DB URL here and let's create a

URL which is poss//

localhost col 5432. as a port number and

then you have to mention your database.

Now this particular URL is pretty common

uh whenever you work with RDBMS. If

you're working with let's say MySQL, you

will say MySQL colost

5430

is no. So for MySQL, the port number

changes. I I think I forgot the port

number for MySQL. I think it's 3306. And

if you you're using Oracle, you have to

put the port number for Oracle which

starts with one and ends with seven. I

forgot the number but you got the point

right? Uh this will change and this will

change but also I want to specify the

username and password I know where I'm

doing that. So there are multiple ways

of doing this because if you click on

create engine okay I'm not able to go

inside it. Okay it's because it's not

able to detect it. So I will import that

as well from SQL alchemy and import

create engine. Okay. Now I should be

able to click it. So you can see it is

asking you for the URL and also you can

pass certain other parameters. Okay. But

I'm not going to pass those things from

here. I mean separately the username

password. I'm going to pass in the URL

itself and yes you can do that. So the

the basic syntax is you mention posgris

SQL col/ slash and then after two slash

you mention your username. For postgris

the default username is posgress itself

and then you give a colon and then you

specify the password. I'm just guessing

the password for this particular machine

is 1 2 3 4 5 6 7 8 for for posgress.

Let's see if it is working or not. And

then you say add the rate. So username

password at the rate localhost colon the

port number/ database. This is the URL

which you have to work with. And the

same URL now you just have to pass it

here. So DB URL and your job is done. By

doing this you are now able to connect

with the database hopefully. Hopefully.

Okay let's keep it as session if that

works. So we got session uh session

maker and these things. Now once you

have your database py file ready, it's

time to go for the next step. The next

step is very simple. Go back to main and

here instead of database connection, we

can create the object for session which

we have done that before or maybe I will

just write DB and I can say session. But

now if you see this is not recognizing

because it's a part of database. I just

have to import this. So come back here

and say from database import

session we can get the access to it and

I think there's no problem. You can see

there's no problem here. And now with

the help of DB you can fire the query as

simple as that. Okay. Once you get the

hold of DB you can fire the query. So I

can say DB dot there's option of query

in which you have to pass the query. Uh

but then what exactly the query I'm

going to pass here? Am I going to write

the actual SQL query? Of course not

because we are using SQL alchemy. So we

I want to use the OM feature of that. I

just have to work with the Python

objects and it should create the query

for me. So if I want to say save it, it

should create the insert query. If I say

fetch, it should create a select query.

The SQL alchemy should do that. But the

question arises nowhere we have done the

mapping for the database and the class.

The class is there. Okay. The class is

there but this class is pilentic. Okay.

And when you try to connect with the SQL

alchemy, it will say okay something is

not matching. It's not my syntax. So you

have to basically create another product

class for the SQL alchemy for the

database. So the database schema will be

created based on that particular class

of product and plus you can mention the

column types. You can mention what

column you're working with column name,

column type and if you want to add some

filters to it or the special access.

Let's say if you want to specify a

particular column as a primary key. So

you can you should be able to do that

here. I mean not here because this is a

parentic based model. You can't

basically add hey this is a primary key.

You have to do that in this separate

class. And also there's no way here you

can change the table name because it's a

pyic again. So you need a class of

product for the pyic for the data

validation and you you need a separate

class of product for the SQL alchemy. So

let's create the class for SQL alchemy

to use. Uh so let's get back here. I

don't know why how this got open. Let's

go get back here and create database

models py. Now this models is for the

pyntic. This is for the database for the

SQL command. Okay. And I'm so lazy. I'll

just copy this because this will be

same. I mean not exactly same similar.

And uh this will change. Now this was

base model from parentic. Instead of

using pyntic base model, I want to use

base from SQL alchemy. Now how SQL

alchemy will know that this product is

supposed to be linked with table or

database is because of this base. Now

what is this base? There's not a inbuilt

keyword. Uh but you have to use

something called base equal to

declarative base and this thing you have

to import. So this function will create

the base for you which you can use to

inhite your class. But you need to

import this. So from SQL alchemy dot

extension dot from declarative it will

import declarative base. Okay. Certain

things you have to remember. So

declarative base comes from this and

once you get this object you can

basically or once you get this class you

can pass it here. And if you go to base

declarative base I'm just checking the

documentation. Okay coming back here. So

once you got this you now this class is

ready to be mapped to the tables. But

then this will not work. We have to do

some changes here. So instead of

specifying type we have to actually

assign the type to it. So you say ID

equal to and now we have to specify

something called column in which you

have to specify all different values. Is

it a integer or a string or is it a

primary key or not or do you want to do

indexing or not? So those thing you can

do with the help of column and that's

why it is different from the model class

the bilentic model but you need to

import this. So from SQL alchemy we'll

import we need column. Now we'll also be

using the type. So let's import that as

well which is integer. Apart from

integer we are going to use two more

types which is string and float. Now if

you remember in the models in fact here

itself. So we got string and float and

int. So we'll import those things here

and this particular class which is

column. So here let's pass in the

constructor. The first thing you have to

pass is it's of type integer. Then you

have to specify do we have to use

primary key. This is a primary key. Yes,

true. T should be capital. And do you

want to do indexing as well for faster

processing? I will say yes. On the

primary key there should be. So this is

how basically you create the primary key

just by mentioning primary equal to

true. And for the other columns, we

don't have to mention everything else.

Just column and the type for it. This

will be of type string. And you have a

choice of adding the indentation for

this as well or indexing for this as

well. So we'll be using equal to column

of type string,

column of type I think it was float and

column of type integer. So these things

we need here. And also you can basically

create or you can add a table name here.

So you can say table name which uh your

SQL alam may be used for storing. So you

can have the same name product or if you

want to have something else you can add

it here. Uh I'll get I will go with the

same name product. And I think that's

it. This looks cool. Now once we have

defined our model I'm expecting that

this should reflect in my database.

Okay. Uh let's see. First of all, we are

not running the front end and back end.

Both are in the stop state. Is it? No,

front end is still running. The back end

is stopped. I can just run the back end.

Okay, back end is running. And now I can

go back to my database. We are using

post posgress and this is PG admin. And

if you have not logged in here, you can

basically click here. It will ask you

for your password. Just just enter that

and then scroll down to your database.

So the database we are using is Cisco.

and make sure you have database because

SQL Alchemy is not going to create

database. It is going to use database

and create tables. So create that table

database by yourself. You can right

click here and say create database.

Simple stuff. Once you get this database

here, expand and go to schemas. This is

where you will find the schemas. And in

schemas, scroll down, go to tables. And

this is where you will see the tables.

But even if I refresh, the tables are

not there. We have done the mapping,

right? table why tables are not there

because nowhere we have mentioning that

hey SQL alchemy you have to create a

table we have to mention that somewhere

so where do we do it let's go back to

main and let's specify somewhere that

hey you are responsible to create the

tables and the way you can do that is by

using the database models okay do we

have to import database models yes so so

import database models okay and once you

have database models you can use your

base now base will say okay I this my

job here was to do the inheritance part

and I' I've done that. Apart from it,

you can also get the meta data of that

particular class product. Now how do you

get the metadata? You just use the

metadata and based on the metadata. So

in this metadata you'll be having a

table name, you'll be having the column

names, you'll be having a type of it and

based on it you will say create all. So

whichever class inheriting base just

create a table and then you will say

binding will be with the engine. There

are multiple ways you can do the binding

you can do with the help of connections

and stuff but we are using engine which

we have created here uh in the database.

This is the engine but this is giving

error because we are not importing

engine. So from database we have to also

import engine. Okay. Now this line will

create the tables for you. But we are

seeing error here. Oh, looks like this

should be small. I don't know why I've

written capital I there. Okay, looks

good. No problem. Now the server is

running. But I want to verify that by

going to the database. Let's refresh the

table. And voila, you can see we got a

table. In this table, we got the

columns. In this column, we got ID,

name. In fact, the best way to see this

is by

uh right clicking on the product and say

view. You can write the SQL query as

well but I'm lazy. So I'll say view data

all rows and you got your table here.

You can say we got ID, name,

description, price and quantity. And

look at the types as well. Additionally,

this is a primary key. Perfect. So table

got created but table is empty. So this

is a query is executing but the table is

empty. You know what we have to do now?

we have to basically save all this

default data in the database so that we

can fire the query. So we don't have the

data in the database. So it's time to do

that. Now what I want to do here is

whatever data you have here I want to

put that in the database. The way we can

do that is and I want to do that only

once. Okay? So every time I open this

application it should check if the table

is empty populate with dummy data. If

you have any data just don't do it. Now

to achieve that I'm going to create a

function which will do that and I will

say this is initate DB initate DB that

makes sense and in this let's do those

steps now. So the first thing we need

here is we need the connection object.

So basically we need to get the session

which we have done before. In fact we

have written that here but we are not

using it. So in fact for some time now I

will just comment this part and we'll

use it later. So once we got the DB

object let's try to add the product. So

for product in products yeah let's try

to add that in the DB so we say DB do

add okay and then in this I have to add

the object of the product okay so I can

simply say product here but there's one

little problem okay so see see what we

are trying to do is get the product from

the list and add it in the database as

simple as that right so this is the code

for this but the problem is the DB is

working with the database model class of

product because this is connected to the

SQL alchemy. But in the code, the

product which we are using is not SQL

alchemy product. It is actually the

model which we have created for with the

help of Pythonic here. And this will not

work. Let me try it out. So let me say

init DB and let's see if this works.

Uh okay. So there is a problem here. So

you can see it says models.product

product is not mapped because this thing

is not mapped but this is mapped. So

that means you can't pass the object of

a product. You have to pass the object

of database dot product object. This is

what you have to pass. That means we

have to find a way to basically convert

this product into the product of the

mapping which is database models. And

how do we do it? It's very simple

actually. You take this product which is

from the pyic and convert that into the

database model. Okay, so this thing has

this feature where it will accept the

key value pair from you and then it will

create the object for it. So if you can

pass that key value pair from the

product, your job is done. Now in order

to do that what you can do is from the

product there's a function called model

dump. Now what this will give you this

will give you a dictionary. So if you

click here uh does it make yeah so you

can see it gives you a dictionary. Okay.

Now once you get this dictionary from

the object so product is the object from

that you are getting the dictionary of

course even dictionary will have a key

value pair but here for this product we

don't need dictionary we need actual key

value pair so how do you convert your

dictionary to key value pair is through

unpacking and in python we know if you

want to do unpacking you use double star

so when we say double star that's

unpacking model dump will give you the

dictionary from the object so let me

reiterate This will give you dictionary

and this will give you key value pair.

And once we do that, there is no issue.

Perfect. And now the application ran. If

I check the tables, if I execute this

query, we're still not working. You know

why it's not working? Because we are

adding but we are not committing.

Because in one of the configuration, we

are mentioning auto commit is false and

that's why it is not running. So what I

will do is I will do the commit and I

will do the commit after the for loop.

Once everything is done I will say db

dot commit and our job is done. Let's

see run and voila. Okay so it's that

simple. Okay so you don't have to write

SQL queries you just say add. It's just

that the only point where we struggle is

when you wanted to add the product and

you have to make sure that you're adding

a product of database models not of

parentic model and uh to you have to

basically convert the parentic object

using model dump which will give you a

dictionary and then you have to unpack

it using star which it will get and this

will just get those values and create

the object for you. So a lot of things

SQL Alchemy is doing for you. It's just

that it's happening behind the scene and

you just have to follow the protocols.

Okay. So this looks good but now we got

an error because again I have saved it.

Now when you save it two times what

happens is it will reload the server and

every time you reload it will basically

execute this the queries and then you

can't have duplicate values right so ID

is a primary key. So you can't have

duplicate values there and that's why

you got error here. So it's trying to

insert but we have a problem. So I don't

want to call this every time uh we load

this. It should do its job only when the

table is empty. So we can basically

check before you do that. So let's say I

can use a count variable and the count

variable is zero by default. And here I

can check if the count is zero. In that

case you do this steps otherwise don't

do it. First I have to fire the query to

database and then it should get returned

the count. To do that I will just say

here db dot query because you have to

pass a query now. So when you want to

fetch you use query if you want to add

you can directly use add method and then

here you have to specify for which

particular table you are passing a

query. In fact you have to specify the

model itself and you you can have

multiple models in your project right so

we'll say database models dot product

and then you will say I want the count.

So this will fire a query which is

select count star from the table which

will give you the count and now this

should not be an issue. So if I save

this code let's see if the server is

running so there's no problem. Okay and

anyway in the normal project we not we

don't even do this right because data

will be already there or maybe you want

to add the data manually. I just wanted

to show you if you want to have initial

data you can do this but with this we

have one little problem. The problem is

with every function like get all methods

or get product by id whenever you want

to use database connection you have to

basically do this line uh db equal to

session and then every time you use this

you are creating a session then you're

not closing it uh that's not a good idea

so what we should be doing is we should

be doing that one place where when you

need it it will use it and then the

connection will be closed and also your

fast API provides a feature of

dependency injection. So we can use that

as well. So now let's see how do you

create this connection once or how do

you write this code once and then you

can use it in all of the methods and

basically we can do the injection there

dependency injection. Okay but uh let's

let's see this. So let's create a

function and I will say get DB as a

function name and the session object

which you are creating will do that here

once of the method accessing this and

when they want the database connection

they should be able to get it and then

they should close the connection. So of

course we have to also close the

connection right and the closing of the

connection should be done after they

have used it. So in that case we have to

use something called eield db and then

after this you will close the

connection. So you will say db do.t

close. So basically this is where we are

creating it. This is where we are

waiting for the others to use it and

then we'll close the connection. But it

might happen something may go wrong with

this. And even if something goes wrong

or if it is not going wrong, I want to

make sure that we are closing the

connection. So if you want to achieve

that, we'll have to say try and we'll

put the close in the finally block so

that it doesn't matter if something goes

wrong here or not, it will close the

connection just to make sure because

resources are very important. So what we

are trying to do here is we'll every

time someone wants to use the database

they will inject this object or this

method there. Now first of all what is

dependency injection is so let's say if

there's a method here which is uh get

all products. Now get all products needs

the object of DB. So basically they want

the session object. So instead of

creating the object here what we can do

is we can tell hey I want this

dependency because I can't work without

this DB. So I want you to give me this

dependency. So the fast API will inject

this object. Okay, that is called

dependency injection. But then this get

all products needs to ask for it. It

will not give you by default. You have

to ask for it. Now how do you ask for

it? So it's simple. You say I want DB of

type session and you have to make sure

that this is not session which we have

created here. And this is something we

have to import from SQL alchemy. So I

will say import

SQL alchemy

and okay so from import you need to get

session so we want DB of type session so

you have to say this depends because

this is where you are specifying that it

depends on something and it depends upon

get DB. So basically it will inject it

here and since we are using dependency

injection we have to also import that in

the fast API. So I'll say depends here

or maybe after fast API anyway it works.

So let's go come back and we got it. So

we got DB session equal to it depends

upon this particular method which is get

DB. So this is how basically you inject

dependencies. Now once you have DB you

you don't have to create this you can

directly use it. So this line we can

avoid now I can directly use it. So how

exactly we are going to use it. Now I

will create products

or maybe I could say products from DB.

So we dB products equal to and we'll use

a DB connection dot and we have to pass

a query which we have done before but

this time instead of getting the count I

want to get uh all the details but of

which type so I will say database models

dot product dotall this will give me all

the products and this is what we need to

return now so DB products simple right

uh now once we have done this it's time

to test it on the server. So go back to

the browser and

refresh this once. And now I'll say try

it out. I want to fetch all the

products. And this should give me all

the products. But then I know you're not

sure is it coming from database or is it

just coming from uh the thing here. What

I'm going to do is I'm going to make the

change in the database. Let's see if

that works. So to change it, I will say

update uh table name is product set. I

want to set one thing. Let's say I want

to change this table to uh laptop table.

So set name is equal to

laptop table where ID is equal to what

is ID? Six. Hope this will work. Yeah,

it it worked. Updated. And now if I say

select start from product execute and

you can see this updated, right? Table

data. Uh table. Okay, we what I have

updated? What's wrong with me? Uh but

okay, I should have said laptop table or