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Hey, welcome back.

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In this video, we're going to do two things.

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First, we're going to test this module, which is still a module, so it's not a package.

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And then the second thing we're going to do is we're going to convert this module into a package.

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So just to refresh your memory, the difference between a module and a package is that a module is one

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single.py file and a package is at least two files put inside a directory.

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So it's better to have a package.

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And I'll explain you why in the second part of this video.

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But for now let's test this module.

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So to test the module it means that it's simple.

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You just have to create a working file.

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So let's say.

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Main dot pi.

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So let's suppose that the user is using your module.

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So they create a file in their Pi charm directory and they want to import invoice.

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So that's how they would do this.

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Now, this works for now because invoice is in the same directory with main.py.

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Right.

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In a real scenario, the user would install invoice from pi.

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Pi.

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Right?

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And then they would import the same way.

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But for testing purposes we don't need to upload it to pi pi yet since we have it here.

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So import invoice and then.

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Invoice that generates.

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And now if the user don't know what to place inside here, you can hover the cursor here and it will

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tell you these parameters.

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Or alternatively you can open a python console import invoice here as well and just do help invoice

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dot generate and that will display you.

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The parameters of the function.

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So invoice path, pdf, path, etcetera.

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If we had a docstring which you can do so you can create here.

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A docstring like that, right?

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PyCharm automatically creates these.

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And then you can also add some extra information, such as?

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This function converts Excel files into or more accurately, invoice Excel files into PDF invoices.

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So save that.

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Now you need to close this console and open it again and do again import invoice.

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And if you do help invoice dot generate, you're going to get that doc string this time.

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As you can see there, and the parameters.

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So that's actual string is displayed in here, plus the generate function with its parameters.

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So now as a user, I can look at here and provide those arguments.

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So the first argument is the path where the Excel files are.

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And for that I'm going to create a new directory here, maybe name it invoices.

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And in that directory I'm going to paste those Excel files.

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I copied that earlier.

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You can find these Excel files attached in the previous video, but also in this video.

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So that folder contains these XLS files.

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And I'm going to just write here invoices, the name of the directory, the PDFs path directory.

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I'm going to create a directory for that as well, like output.

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Although we could improve this part by going to invoice and.

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Saying here that.

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So at the very end here, at the last two lines, we say if OS dot path, dot exists, PDFs, path,

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colon and then indent this actually it should be not if not.

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So if the path does not exist, we create it.

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Right.

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So that means the user doesn't need to create a output folder here.

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They just want to declare what name they want their new folder to have and Python will create it for

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them.

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If it doesn't exist, so then the image path, if you have an image, you can find a PNG image attached

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in the previous video or this one as well.

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And I want you to please paste that image in the root directory of the project.

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So here it is, Python.

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Hello, dot PNG in the root directory and I'm going to specify that name here.

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Python.

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Hello.

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Dot PNG.

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Then we want to specify the names of the columns.

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So for that we need to look at our Excel file.

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So product ID, product name in the given order product ID.

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I'll split this line here.

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Product Underscore Name.

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Then we have amount purchased.

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Then we have price per unit and total price.

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Price underscore per unit.

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And.

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Total price.

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So, yeah, that's it.

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That's about the arguments and that's how the user would use this library.

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So now we're ready to call this run main.

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This obviously needs this library open Pi XL, which normally it will be installed as a dependency when

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the user installs the invoice package.

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But since we are locally now, we need to install it separately using Pip install open pi XL.

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So this is to read.

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This is needed to read xls X files and let's run again.

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This time no errors.

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So let's see.

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Output and yeah, it seems to be working.

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So the testing of the library was successful.

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Now let's convert this library, which is actually a module into a package.

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So we use the words library module and package Library refers to either a module or a package, and

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a module is just one file as it is now.

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So it's just one file.

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Please ignore.

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These directories.

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So these are for testing only, but our module has only one.

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PY file.

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So if we wanted to add more codes in the future, let's say we want to expand our code.

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To also convert the Excel files into HTML.

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So for that we would need to add another function, right?

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But it would be better to have that function in a separate file, not inside invoice.py, but somewhere

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else.

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And in that case we would need a package because a package is more than one module.

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So currently we have the invoice.py module and a package would be a directory with multiple modules

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inside.

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So let's turn this into a package.

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Even though we only have one function at for now for the sake of scalability.

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So to prepare for the scenario when we want to add more codes later, we want to convert this into a

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package right now.

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So to do that, you want to create a new folder in your root directory, let's call our package invoicing,

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perhaps invoicing.

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Right.

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And you want to drag invoice.py to invoicing and press on refactor here.

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And so now we have a package with one module inside and if you want to add more modules later, you

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can go to new and create a new python file.

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Right now a good practice is to have.

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Eight.

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Underscore.

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Underscore init.

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Underscore.

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Underscore dot pi file in invoicing.

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So press enter and that will create this dot pi file.

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Why is this a good practice?

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This was mandatory actually before python 3.3.

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If you wanted that folder to behave as a package, you would have to have this file.

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Now, it's not necessary, but sometimes it's still good to have it because you can import in any dot

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pi things from invoice dot pi.

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Let me talk about that in one minute.

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But now that we have this invoicing package, we can go here and we would need to import it as from

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invoicing import invoice.

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You see PyCharm updated this line automatically because before it was just import invoice.

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So when we moved invoice to invoicing PyCharm refactored all the projects.

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So now we have this.

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So with the package, the import statement would be different as you can see you say from invoicing

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import invoice.

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Now you cannot do for example from invoicing, import generate, right?

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So if I run this I'm going to get an error cannot import name generate because invoicing doesn't have

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a name generate here.

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Right.

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But if you want users to be able to import generate like that, you should go to init.py and do from

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dot invoice.

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So we're inside invoicing here, right?

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Import generate.

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And now as a user, you can successfully execute this code.

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So that's the purpose of the init file.

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Basically, you can make available certain names at the level of the package, right?

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So.

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As you can see from invoices, import generates.

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So you skipped this module and you made available that function or that module like that.

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So this is not usually the case, but if you need to do that, that's how you do it.

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And yeah, that's our package invoicing.

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And now we can delete these files from our project because in the next video we're going to upload the

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package to pypi.

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So I'm deleting all those testing files and also main.py.

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So I'm going to keep only the package with init insights invoice.py and the image here.

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Also the image we don't need because it was part of testing.

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So just the package directory within it and invoice.py and yeah, that's about this video.

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Let's upload the package to py py.

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In the next video.

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See you.