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- [Instructor] Being able to read CSV files

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is only half the equation.

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We need to be able to write CSV data as well.

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The CSV module provides a set of classes

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and functions for doing exactly that.

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So in this example, we're going to see

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how to write data that is in an array format,

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and we'll see how to write dictionary data

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in a separate video.

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So for this example, let's open up write_csv_array.py.

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And for this example, you can see

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that I've already got some code

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that defines an array of rows of data.

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The first row is the header information,

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and the rest of the rows contain lists

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of different food types and prices.

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It's essentially a subset of the inventory file

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that we've been working with in the chapter.

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So let's write a function

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that will write the data to a CSV file.

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So let's declare the function,

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and we'll call it write_array_to_csv.

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And that will take in the data to write

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along with a filename.

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Then all we need to do

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is open the file that we want to write to.

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So I'll use my with open statement,

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and I'll pass in the filename.

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And this time I'm going to use write mode.

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And I'm going to specify the new line

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is equal to an empty space,

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which means write out the line endings

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according to what your operating system prefers.

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And I'll open that as csvfile.

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And then we just need to write the data.

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So I'm going to make a variable called writer,

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and I'll create a csv.writer object

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with the CSV file I just opened.

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And using that writer, I'm going to call writerows

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to write multiple rows of data.

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And that's pretty much all there is to it.

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You can see it's a little easier than reading the data.

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So all we need to do now is call that function.

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So let's call write_array_to_csv,

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and we'll pass in my data array,

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which is defined right here.

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And we'll give it a name.

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We'll call it output.csv.

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All right, so let's save

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and let's try running this.

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All right, and when I run this,

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you can see that over here in the sidebar

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a little output.csv file has shown up.

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So let's click on it.

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And sure enough, it contains the data from the array.