Our models have five really useful methods that we'll be using a lot.

Create, adds a new record to the table.

Select, let's us pick rows out of the table to use.

Save, will update an existing row in the database.

Get, will fetch a single record from the database.

And finally, delete_instance will delete a row from a table.

There are many other methods on Peewee models but I leave them for

you to read about in the docs linked in the teacher's notes.

Okay. So let's setup some of the info that we

want to have inserted into our database.

Like I said, we're gonna use a dictionary to hold on to all the data.

And the reason for

that is because a dictionary is easy to look back to, it's easy to update.

We can play around with it.

We've all had a lot of experiences with databases or dictionaries.

So, not anything crazy.

So, I'm actually gonna make a list for all the students and

then a dictionary per student.

So, let's make a username and then I'm gonna say,

Kennethlove, and we'll say points and 4888.

All right.

And then username.

Chalkers, points.

[BLANK_AUDIO].

Username.

[BLANK_AUDIO]

If you've explored the collections library,

then this is actually a really great place to use something like named tuple.

This is also something where we probably could have done a dictionary where

each key is the username, and the points are their value.

But this is a little bit more obvious of how we're going to

put things into the database in the end.

And [INAUDIBLE].

Dave has a lot of points.

All right.

So, here's our dictionary or our list of dictionaries, rather.

So you can see, we've got two keys for every one of them, we've got username key

and we've got a points key for each one of them, and then they have a value that has

their username or their points, depending on which key it is.

So, let's add a function that will go through all of these,

and add them to our database, and let's call it add students.

And what we wanna do in here is, we wanna go through each student in students, and

we wanna use our modal, which is called Student, and I'm gonna call create.

And we're gonna say the user name is equal to the student username.

And the points is equal to the student points.

All right, so now let's come down here to our if name block and

let's add that in, so down here we wanna call add students.

'Kay.

So, let's try running this.

Python students.py.

Okay, no problems.

This is all great and wonderful until we run it again.

Look at this. We've got all, we got tons and

tons of these integrity errors.

Now, why did we get those?

We got those because, remember we made our username unique.

And what we're doing down here is a create.

We're saying, put in a new row for every single one of these.

So the first time through it puts in that new row for Kenneth Love.

And everything's cool, everything's copacetic.

The second time it comes through, it says hey, put in a row for

Kenneth Love, and the database says, no wait, I can't, I already have

a row where the username is Kenneth Love, I can't do a new one, because it's unique.

So let's change this, and

the way that we're gonna change this, is we're gonna do a tri-block.

Oops.

So we can indent that.

So we're gonna try to insert the the student.

And you notice that we're getting this integrity error down here in our

error messages.

So we're gonna except IntegrityError.

So if we get an integrity error, then let's do student_record.

Oops, student_record equals Student.get, username equals student, username.

Right, so we wanna get that student, it must exist, so we wanna get that student.

And then we want to do student_record.points equals

student points.

So set their points to the new one, and then student_record.save.

So, get the student out of the database.

Change the points to whatever the points is now.

If it's changed, it may not have changed.

But just set it to whatever it is now, and then save the record.

Now we can make this smarter,

as I just mentioned, by making it check to see if the points is different.

I'm gonna leave that up to you.

But that would be a good thing to do.

All right, so now, let's add another new function.

Actually, let's go ahead and test this one first.

Let's do Save.

Let's come back down here.

We should be able to run this again.

No complaints, great.

'Kay, so now let's make a new function that is

going to get our top performing student.

I want the student that has the, the highest number of points.

So we'll call this top student and

we'll say student equal student, our modal.select.

So what that does is that gets all of the students.

We've got all of the student records that are in the database, 'kay?

We don't want all of them, we just want the best one.

So let's do an order by, so let's sort them and

we're gonna sort them by the points attribute, right?

We wanna sort by whoever has the most points.

And we wanted to do this in descending order, so

we want the biggest number first, the smallest number last.

Ascending would be the other way around where we have the smallest number first

and the biggest number last.

So descending, it gets smaller.

Ascending, it gets bigger.

So let's add one more thing to this.

What we can do is we can say .get on the end of this.

And that's going to only get us the first record that comes back.

So we've got all the students.

Sort them all by their points so

that the biggest number comes first, and then get the first record.

I know there's a lot there, but that's what it is.

Okay.

So, let's return a student.username.

Actually, you know what?

Let's just return student.

Okay?

And so, what I wanna do is down here, after I add the students,

I want to print our top student right now is.

And then I'm gonna do a format here where I call top_student.

And so let's actually go here and do 0.username.

Cuz zero is whatever comes back from this, and

we know that has a username attribute so we're gonna print out 0.username.

All right, so moment of truth, let's give this a try.

oh.

I forgot a parenthesis.

All right, now let's try it.

Our top student right now is Dave Mcfarland.

Sweet.

Dave's got a lot of points.

Let's go change that.

Dave's got a whole bunch of points, but I wanna be the top student.

So, whatever Dave has, plus 1.

Okay, so now if I run this, it should come back as me being the top student.

Great, it did.

Now why did it change to me?

Just in case you didn't catch this part yet, it's because of this.

We had the integrity error,

there's already a row for me, so now we grab my student record,

update my points to whatever's in the dictionary, and we save it again.

Then when we run top student, it's gonna select my record.

So that's pretty awesome.

We're able to get our students from the dictionary.

Stick them into the database.

Select them, order them, pick out just one top one.

And then we were even able to update and change those records afterwards.

This work, creating, reading, updating, and deleting records is known as CRUD.

It's the backbone of pretty much any application that deals with a lot of data.

I can see you're getting antsy to build something real already.

Well, that's great because our next step is to start the real reason we're here.

A command line diary application.

We'll do that in the next stage.