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Hi again.

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And we can't consider this lecture as the last lecture about building our Web application,

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but we still have something more to do.

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We have to deploy our Web application on a live server so that we can visit that through you URL.

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Because for now, as you know, this is just running on our local computer.

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And yeah, the lecture is a short one.

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So I'm just going to calculate the average height out of the data base table and then send that average

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back to the user e-mail address.

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So let's do that. This is our send_email.py script.

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And we have to calculate that somewhere here in our main Python script.

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And how do we go about calculating an average out of the database table field?

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Well'd need all the values of that field.

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So that means we're talking about a query.

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And so when should we do that query?

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Well, we want to calculate the average.

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We also want to include the data of the current user to that average.

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Which means the data that this user is entering in their session.

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And yeah, we can see that here we are sending the user data to the database.

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So we are committing the changes to our database table.

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And that suggests we can calculate an average just of that statement.

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So here.

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Let's create a variable where we'll restore the average value.

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Let's say average_height.

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That would be equal to, again, db.session.query.

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And in this case, we need to apply an average function that the average function is made available

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by

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the core sqlalchemy library, which we have already installed. And the sql class.

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And we need func

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from the sql class

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of this library.

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And once we have done that, we you don't here in our query.

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And then we can set the arguments of our query.

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We can pass here the table field that we want to query.

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That'd be data.height.

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With an underscore.

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But we don't need the entire field.

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We only need the average data.

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Dot height_.

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So, again, the average methods of this class, which we imported out of sqlalchemy.

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And, you know, we are almost ready to send these average value to the send_email function.

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So that the send_email function sends the email to the user with that average so we can incorporate that

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here.

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But before we do that, it's good to make sure this statement here is working well.

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So print average_height.

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Save script.

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I have an invalid syntax there.

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You probably notice that I didn't write import here.

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I didn't notice that.

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And try again.

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Now it's working, so maybe reload the page and let's just enter some dummy data there.

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We just need to know this print function is producing the correct output.

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So b.com.

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And let me zoom out the page.

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Okay.

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I hope you see it and 176. Submit.

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The Web app is working smoothly as we can see it.

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And let's look at this line that is being printed in here.

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As you can see, this is not a number, so not exactly what we were expecting.

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This is an sql statement.

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Python is printing that out.

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We need to do a trick here again.

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And what that trick does is it applies this scalar() method to this object.

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So to this sql statement. Dot scalar with brackets and you don't pass anything in there.

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And what they do, do is it will extract the scalar 

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out of this statement and a scalar is just a number.

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So nothing fancy about that.

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Save the script.

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I'll try this again.

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Maybe c@b.com this time.

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And yet now we can see the actual average.

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So it's 176.

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But we have quite a lot of decimal points in there.

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And we surely don't want to send that number to the user

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as an e-mail.

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Let's apply something in there.

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And here, what I would do is apply a round function.

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And so average height equals to round the current average height.

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So what that will do, it will around of this number to one decimal point.

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Or if you leave this empty, it will just up the number without any decimal points, or you can go off

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to two or three or whatever you want.

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Good.

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And yeah, that should do it.

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D this

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time @b.com.

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Let me try another value.

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Let's say 200 and submit.

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Yeah, this is the average by adding 200 there, I increase the average from 176

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to 182 centimeters cm in the case of my application.

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Maybe you're using some different units there.

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Yeah, I think this is all clear.

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And let's go ahead now and send these average high value to the email function as well so that the email

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function, then we'll do something like average, let's call this avarage_height as well.

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So it's just a parameter.

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It would be a local variable in here.

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It doesn't have to be the same as this one.

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Good, average height.

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So we could do something like average height.

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Let me maximize this.

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O all is a placeholder, maybe a period there than inside the tuple

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we pass the first variable for the first placeholder and the second valuable variable for the second

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placeholder.

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That should do it.

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Oh, we're almost done there, except of if we let me save this and resize this.

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So, yes, we're almost done, except this function is being called before we even check for an existing

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e-mail address in our database, which means if we pass

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now, if we pass average_height there, we average calculated by these two statements wouldn't make much

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sense because we haven't calculated the average height just yet.

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We don't want to send the user an average without getting their data as well.

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They height

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Which means we take this statement, called it from there and put it in here.

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In here.

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Make sure you indented just like that.

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No.

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So email_height, average_height.

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And we send those three in here.

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And, you know, we could also calculate something very quickly here, which is the count

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and db.session.

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I'll explain that in a minute.

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Query and data.height.

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And give me the count.

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So what we're actually counting are the height values that we have in our database table.

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Why would you want that?

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Well, you use something, the average value to the users, but they may also want to have an idea of

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how statistically significant is this value.

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Like, if you have three values collected in total, that wouldn't make much sense to say, like the

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average value of population or whatever is this one here.

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So it's good to send the user count, actually, which we were calculating in here.

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So up here, we did almost the same thing, but here we applied a filter.

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So we filter only those rows where the data.email, the value of this field was equal to the email

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address that the user was entering in that session.

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But here we are getting all the rows.

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So count.

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And then we pass that to the function call.

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Count.

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Also in here.

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Count. You're not seeing these.

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So let me do View, Toggle Soft Wrap.

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And now we have the average height of all.

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Is.

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Is this value here and that is calculated out of this number of users of people?

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Maybe.

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And you can't hear that looks good almost.

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We can also make these bold, strong, they're

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strong here, strong.

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They're there as well.

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Good.

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Finally, I'll say this.

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See if we get any syntax error there.

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No.

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Everything looks good, and, boy, save this as well.

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I think it's now safe to test through the application, but in order to get that email, you want to

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make sure you are using an email address that you haven't used before in your in that application.

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So you don't want to send the next e-mail address.

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I'll make sure this is a database to collect it and go to school and you'd want to delete.

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So if I do select all for all data, there's there's a table.

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You'll see that I have this my email address there.

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And I want to delete that to delete from data aware email.

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So the name of the field and you want to use single quotes.

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So e-mail is equal to my Hotmail address.

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Yeah.

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Execute.

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That's Waldo affected.

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I can prove that data.

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Yeah, my Hotmail addresses.

165
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No, they're not.

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So I can go ahead and

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try this.

168
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No, I'm

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good.

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Solid.

171
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I have an error there.

172
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Uh, Dutil has no attribute highlight because in here that should be another school.

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Mm hmm.

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So that's the name of the column, as you can see in here.

175
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So it's high with another school.

176
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Yeah.

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Sorry for that.

178
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The errors happen all the time.

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Mm.

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Go back again.

181
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If I try this again, it seems like we've got something from that e-mail address.

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All right.

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So at least we know that when we enter an existing e-mail address that is not working yet.

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I have to go here again and delete from Dotel where mail equals to.

185
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So this is a query here and execute Wataru affected.

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Good.

187
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Oh, let me try this again.

188
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I hope this will work this time.

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Submit.

190
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Thank you for your submission.

191
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Now, why should expect an e-mail?

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That was quick.

193
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Hey, there you are, Heidi, swell, 76.

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Average height of all is this.

195
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That is calculated on or five people.

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And we're done with our application.

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Sorry.

198
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That was too much.

199
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But I believe we did quite a lot of things through all the lectures.

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The good part of this is that you can modify this application.

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This is highly customizable.

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You can customize this.

203
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You can tweak it.

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And you can adjust it so that you gather your own data or any other information that you get.

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You may might be interested on any of these scraps of these instructions.

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But the next lecture, I'll show you how to get this application, have database and deployed on a life

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server.

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Quite interesting.

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Yeah.

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Talk to you in the next lecture.