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Welcome back. So now let us add the function to allow our users to log in.

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So I'm gonna say the fine and let's go

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with the login uh underscore will be the username.

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Let's add a colon. Actually, let's add a note. Ok? And we can just say login function

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and there you go. All right.

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So in order for the user to log in,

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they're going to require the username and the password.

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So

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let us start by saying username equals and then input

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in brackets codes, enter your username colon.

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OK?

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And then we can also add the password equals input brackets,

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enter your password.

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And there you go. All right.

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Now, in order

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to verify that the username and password do exist,

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we're gonna have to open up our users dot

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TXT file. So I'm gonna say with

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open

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and now in brackets, what's the name of the file? It is users dot

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TXT.

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And then what is the mode

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that we're going with? We're going with the read mode.

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OK? Because we want to read from the file

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and I'm gonna say as file

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colon.

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And now let us create a verbal called users

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that would accept the file dot Readlines function because remember

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we're gonna have to read line by line from each user

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in the users dot text file. So

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I'll say users equals to file

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dot Readlines and now

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brackets and there it is. So now we need to check if the

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credentials match any stored record.

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So what are we gonna do? We're gonna create our for loop.

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So I'm gonna say four,

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let us use the variable user in users.

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OK?

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So now

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what do we want to check? We want to check for the user name and then the password.

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So we can create two variables in here. We can go with this stored,

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OK? Stored underscore

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username

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and then comma we can also go with stored

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underscore password, right? A lot of creates two variables to represent

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the store username and then the store password.

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And now how would we check?

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We need to first of all

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check to see if the user name is correct

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and then also the password. But now take a look at this. Ok.

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The users dot CX file as it is we have Alex and then colon Alex. So

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we need to figure out a way how we can separate the user name from the password.

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And we know that it's the colon, the colon symbol that separates them.

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So we can use the split function

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to separate the user name and the password.

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But we can also use the strip function remember the strip function,

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we use that to remove any white characters or empty spaces, things like that. Ok.

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So let's go back in here. So what we're gonna do right now is I'm going to say user

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and now let us add the strip function

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to remove all the necessary space from the username.

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Ok.

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Our brackets. And now I'm going to add the split function.

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And what are we splitting the username and the password by is going to be the colon.

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And there you go. So we're gonna split the username and the password by the colon.

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So from here right now,

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we can check,

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we can say if

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the username

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is the same

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as what the store

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underscore username

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and what and password

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is equal as what is stored underscore

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password.

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What do we want to do?

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We want to print

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and say

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log in

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successful

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and there you go.

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Awesome. Awesome. Awesome. And then from here,

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we can simply return for now. Ok, later on we will add

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additional functionality. But for now, let's just return

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and go back to the beginning of the program. So we're going to exit the function

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after a successful login.

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And of course, we can also print just in case something

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did not go correctly.

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We can print

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nine brackets.

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We can simply say invalid

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username or

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password.

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And

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there you go, let me just add

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some space in here

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and there we go. So hopefully this should work let me

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integrate it into the main function. So what we want to do right now is

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where it says the

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choice number two,

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we can remove the print statements and now simply add

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the name of the function which is login under

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user

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and now brackets and there it is OK,

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fingers crossed. Let us run the program

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and let us see.

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I'm gonna go straight to log in because

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we've already created the Alex username and password.

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So,

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user name is Alex, password is Alex. And there you go. Awesome. Login successful.

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Let us try to see if we'll accept

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a different username that doesn't exist. So

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I'm gonna go with login and let's go with Philip

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enter password, sword fish.

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And there we go, it says invalid username or password. So it is working. Awesome.

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Awesome. Awesome.

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So we've successfully added the registration function.

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We've successfully added the login function as well.

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So now join me in the very next video where

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we're going to advance the program by introducing the password checker

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that will ensure that the password created meets a certain strength criteria.

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I'll see you then.