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Hi, welcome back in this video, we will program a fire destroyer, so that's a nap, which is useful

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if you have sensitive files in your computer, which you really want to permanently delete.

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And it's not simply about deleting, but it's about destroying them by overwriting them.

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Now, if you follow the course, we did have a lecture where we wrote a script without a graphical user

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interface, a jisa script which runs on the command line.

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So this script towards idiots is you specifying a folder in that script, for example, destination

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is a folder in here which may contain some files.

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And so the script then eight reads over that path object.

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So for path in that directory, it filters all the CSC files and then it opens each of that path, file

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path, and then it overrides an empty bytes string into that file.

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So basically, each file will be overwritten with some empty contents, and that's makes the file hard

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to recover if somebody else gets your computer and they try to recover your hard disk.

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Previous content because the file will be overridden by Python.

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And then finally, with the lead, that overwritten file.

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So first we overwrite, and then we deleted.

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This is a script that does this, but now we want to take this one step further and build a graphical

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user interface.

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So this is what we have built and this video and it has this description here.

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Select the files you want to destroy.

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And it was the user that the files of the permanently deleted.

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And then it has these two buttons over files, which shows you a file dialog.

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So here you can select multiple files that you want to delete.

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For example, these three open them and the program.

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The cooee will display the paths of those files in here, and then you can see destroy files and this

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destruction successful string shows up in here and the files will disappear from that folder so they

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will be overridden by Python and then deleted.

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So let's run this program.

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We will use PI two six.

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So if you have any solid, please do so with Pi Q to six people.

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Install Pi two two six seven.

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I'm going to use this code.

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So we did sort of write this code previously.

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And this creates an application instance.

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It creates a window instance as well, which is where all the widgets will be added to the buttons of

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the labels of text.

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So whatever you add to your main window of your green.

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So we said the title for the window.

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Oh, we also need a layout which is equal to Q the box layout, and you need to import that in here.

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Cuvee box layout.

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So we set then.

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That's the layout and use parentheses here as well.

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And then we said that layout as the main layout of the window will show the window and then we execute

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the app instance so that it generates our application.

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So currently, this is our winter looks like it has this title.

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And so we are ready to add widgets now.

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So we said that first we're going to have you're on top a label, so let's add a label for that.

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We need to label the Q label widgets.

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Let's say description is a sequel to Q label, and then we add some info here, which goes inside quotes,

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so it's a string using single quotes here and I'm going to paste the string, which I wrote previously.

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So what this is is select the fast you want to destroy.

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I'm telling the user what the app is about and how they can use it, and then the files will be permanently

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deleted and permanently is in red phones so you can use these simple tags as you see in here.

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So red's a acing double quotes.

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That's why I use single quotes for this since I was using double quotes.

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So the string, once you have created the label object, then you want to add the label to layout.

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So layout that at widgets and description is the label, and let's see what we have.

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Yeah, so that's the label and permanently is in red color.

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So as we develop this program, I'm going to introduce you to advanced concepts of PI cutesy, such

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as this styling of texting here, and we have more and more concepts to discover in this video.

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So let's add more widgets.

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What's next?

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Well, it has to be a button.

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So let's say open beta and a sequel to Q.

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Well, we need to import the button.

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So let's not have that line infinitely long and have another import statement here from public six.

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That's cutesy widgets.

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Import queue push button.

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Q push button goes there, and the title of the button will be open files.

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Adverts, bots and to layouts using and widgets open bottom tested.

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Yeah, is there?

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No.

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If you want to add a tip option feature to this bottom, you can do so because currently, as you see,

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when I offer the mouse over the button, I don't see any info popping up.

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So if you want to have that, then you want to refer to the variable associated to your button object

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and then say sets to tip.

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And you can use the same string open files and run.

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So if I hover the most button, here you see this small prompt open file.

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This could be useful, especially when you have icons instead of buttons with text so icons don't have

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labels, and it becomes very crucial to have these popups so that the user can see what these icons

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are in bold.

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However, this is not an icon is just a button with plain text.

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So perhaps this is not necessary in this case, but it's just there so that you know that this exists.

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And do you want to make the button maybe smaller?

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Well, you can do that by referring again to the bottom and then you set fixed width.

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So with that, let's say 60 and run.

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So it's too small.

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Perhaps a hundred so this.

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Run.

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Now it looks better, so try to experiment with other sizes.

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And let's also align the button to be the center of the window for that, you can use alignment equal

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to so alignment inside the ads widget method that will be equal to cutesy alignment and cutesy is something

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that needs to be imported from pie cute six dot cuticle import.

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So alignment flag and that's a center property.

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Varun and the botanist of the Sentinel.

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Right.

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So what does this button do?

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Well, that's connected to a slots, which will be a function of that.

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We will do right on top here.

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So to connect the button, you should refer to the button.

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So we're talking about doing something when the button is clicked.

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So open button that's clicked, then we connected to a function.

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So when the button is clicked, this function now will be cold.

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Let's name this function open files and then define that function.

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Open files in here.

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And so what should the app do when we press the open files button?

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When the user presses that button well, the app should open a dialog box that allows the user to select

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files on their file system on their operating system.

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So for that, we need something called Q File dialog, and so you need to import that.

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And here and then create that object instance.

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So for that, I'm going to say file names and just another score.

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So we have two variables here, and these two variables are equal to Q file dialog.

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I'm having two variables because this returns to objects.

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The first object is a list of file names.

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So if the user selects three files than a list will be generated containing the absolute paths of all

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those files of each of those files.

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And then we have this, which is some extra information about the dialogue action, which we don't need.

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So it's we just leave it as an underscore, which is just a variable, but it's just a throwaway variable.

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So queue file dialog.

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Actually, we need to call the get open file names of that class.

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The first argument will be the window, a window is the variable that contains a cue widgets object

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and then you won't specify a label for the dialog window.

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Let's say select files, and that's it.

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Now, just to show you what file names is, I'm going to print it out on the terminal and then I'll

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select some files, not through the green.

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But first, make sure you have some sample files that you want to destroy.

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So open your file explorer, perhaps put some simple files which you don't need there.

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So putting one here, one file, I'm going to just duplicated copy and paste control of reconstruct

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the make several copies.

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So you have some files to to play around with and then run the code and open files.

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The dialog will appear.

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Go to the folder where you have those files.

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Those sample files and selects.

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A couple of them open.

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And now when you pressed the open button on the terminal, I got a list printed out of the lease has

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three items and each item is the absolute path to each of those files that we selected in the dialog

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box.

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So that gives us snow, the possibility to manipulate and lead those files.

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So for that, I'm going to write here a loop for file name and file names.

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And I prefer to use the path library.

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So from path lib.

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It's a standard library.

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You don't need to install its import path.

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So I'm going to convert each file name into a path object.

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A path is a specialized object in Python, which makes dealing with files more efficient.

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So path is legal to path.

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That's class.

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And then we provide file name here.

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That's file name, which in the first loop will be that first string.

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So file name is just a string and file name goes inside the path and it becomes like path object now,

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not a string.

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So and then we say with open path, that's current path object, we open, it's as a right binary and

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we say as file.

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So file now is an open file in Python.

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It's a specific file object.

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So we have a string in file name.

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We have a we have a path object in path and we have a file object in file.

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And this file we can write a bytes string.

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So the file is open now and we can modify it with Python.

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So what we do is write a bi string there and that will overwrite whatever content the file has inside.

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So that's like modifying the file and the previous content is just lost.

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So that's a very safe deletion of your sensitive files.

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So with that, you write the file, so you modified.

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Then if you want to delete that overwritten file, you can do so by using a first, you have to on indent.

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So the file will be saved on disk at that point.

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And then if you want, you can save Path Dot on a link to delete the file.

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The Unlink method will delete that path.

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So the file associated with that path object.

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So let me try to run the code.

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And then click on open files, go to the Files Directory, where I have these files, I'm selecting

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a two, three and four and press on open.

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So with that, if I go to this directory now, I see that files two, three and four are gone.

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So they are overwritten and then deleted.

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But this is not the best user interface because I think we are missing a button here.

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So if you run the program again, the best user experience is that the user first should open the files

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so they select the files they want to delete.

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And then here should be another bottom that should they should say something like destroy the files

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and then bots and should execute this part of the code, not the open files button.

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So what we need is another bulletin under the open button.

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So let's say destroy button between a sequel to Cute.

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Push a button, and let's name this this trolley files, let's it's a width four, that's a swirl and

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puts it at the center here.

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And then finally, make sure you change these from open button to destroy bottom.

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And also here destroy button.

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And then finally, you referred to destroy boats and to collect to connect.

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And we want to connect that to another function.

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Let's say this throwing files.

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This is a new function.

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We need to write somewhere in here define destroy files.

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And then this code.

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Is transferred to this function so that this code executes when the user presses that destroyed button.

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But we have a problem here.

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File names is a variable defined inside this function and that makes the that's the variable local.

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So it only has a scope inside this function.

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It will not be recognized outside of that function unless we declare that as a global variable.

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Now, using global, so making variable global in Python is not the best practice.

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And this could cause some issues later on when you expand your program unless you are very, very careful

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with what you're doing.

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And you can avoid those problems.

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But the best practice to avoid using global variables is to use object oriented programming.

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So to structure your programs using classes and you can do that with Piketty, so you can use classes

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and you can write the same program using classes and avoids using globals because inside that class,

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you can use instant variables instead of global variables.

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And that would solve the issue with not having to use global variables.

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So that's something you should know about using global.

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With that in mind, let's keep our current structure without going to object oriented programming.

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So this will do the job just fine.

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So by doing global file names, that means the final names can be accessed now from other parts of the

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court and not only inside from inside this function.

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So let's try to run the code again.

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Ron, Maine, now we have this button here.

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So first, we want to open files.

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Let's select five and six open.

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Press on destroy and check.

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If fires are still there or not.

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Yeah, so they are destroyed five and six.

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We can do more by adding a label under the lost bolts in here so that we let the user know what's going

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on.

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So what I'll do is I'll go down here and at.

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A message valuable, which a sequel to Q label cannot of this will be empty, and I'll add this to the

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layout.

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So now that the widget's message of I'm in here was the user opens the file instead of printing all

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the files and the file names on the terminal.

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I want to print them out all that's labeled so message dot set text and then you want to enter file

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names, notes file names because file names, as currently you know, it's an it's a full list which

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looks something like that A, B and C and so on.

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So a list cannot be accepted by the set text method.

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So what we want to do instead is we want to see him join.

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So I string that join the file names and what we do we want to join them with.

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You can see a dash, for example, and you'll get something like that, a Dash B or you can do better

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and see backslash, which creates a brake line.

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Well, here on the terminal, it doesn't look like a brake line, but if you printed out on on a label

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widgets or use a print function here, then you will see that.

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So it will be a brake line.

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So Max, listen, now you see, that's a one line, and then we have the brake line, which connects

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the two so backslash and is converted into a brake line when you use a print function or when you print

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it out on a label.

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So that means we should say backslash and dot join.

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So join all the elements or file names using that separator.

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And then in here we exit the loop.

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So in this?

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Place in here in the same indentation label with a for loop, and that's a message that sent text destruction

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successful and run.

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So open files and select a few files.

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Seven, eight, nine using the shift, and so these are the files that were selected.

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And you press on destroy files and you have Vats labeled destruction successful.

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You can put the label more on the censor by using alignment.

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A sequel to Kutty, that alignment flag, that's a line censor and that should solve the issue.

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So open files.

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And now the label is at the center.

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So that concludes this video.

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Thanks a lot for falling and to see you in the next videos.