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(upbeat music)

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- [Instructor] All right, it is time to try

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a programming challenge with what we've learned.

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For this challenge, you are going to write a program

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that reads the contents of the inventory.csv file,

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and you're going to add another column

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to the data programmatically.

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So if we look at the CSV file,

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there are two columns for prices, right?

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One for wholesale and one for consumer price.

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You're going to add a column named margin

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that will contain the difference

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between the consumer and wholesale prices.

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This means that you'll add another header

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and then write out the updated rows.

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So I'm going to run my finished example

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so you can see what the results should look like.

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I'm going to right click

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and run my example here in the terminal.

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Alright, so when I run my code,

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you can see that the output file is created here

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and when we look at the content,

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you can see that there's a new column called margin,

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and there's a new column of values

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that contain the difference

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between the consumer price and the wholesale price.

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So that's the challenge.

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Go ahead, give it a try

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and I'll explain my code and how I solved it.

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If you want a hint, then keep watching for a little longer,

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otherwise, stop the video here,

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go ahead and get started with the challenge.

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All right?

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Okay, do you want the hint?

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Are you sure you want the hint?

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Last chance.

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All right, here's the hint.

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When you read a CSV file,

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all of the values are going to be read as strings,

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so you're going to have to find a way

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to convert the consumer price and wholesale prices

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from a string into a number, okay?

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So that's the hint.

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Go ahead, fire up Google search if you need to,

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and good luck on the challenge.

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I'll see you in the next video.