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Hello and welcome to the.

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Part 3 of creatine a calculator with Python before we carry on.

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From where we stop I just want us to quickly look at the code we have so far.

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So he started off creating a class.

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Then we have a few functions here created a functions called on to score in it and we initialized the

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frame.

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So the master here basically is the main window of the application we had created a class called widgets.

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And here we have the different buttons created as widgets.

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So most of the code within the buttons are the same.

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The E course to button this is the coastal button here.

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Here we have where we've got these sticky said this ticket equals W..

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We've got a column span to two.

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Normally when a widget occupies one cell in the grid you can also grab multiple cells of a row and merge

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them into one largest cell by setting the column span.

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Option two equals to the number of cells.

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So we've used the column span here and also here.

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We've used a command.

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Notice we didn't use lambda in there.

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Here we've used a command.

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And we've said that to serve the glad display what this would do.

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When you click on the color button it will clear the display on the screen.

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So that's what that will do.

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Also here we used this self dot task.

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We've set that to blank.

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Basically a task is a subclass of future of a future a future basically is an object that is supposed

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to have a result in the future.

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And the task is a subclass of that future.

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So let's go ahead and create a few more methods of func during the creation of the buttons we used we

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attached it to the bottom the click method which we haven't created some have now created it here and

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the button click method here.

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So it takes in the Self Variable hand the number that the user inputs into the calculator.

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So here this is the logic.

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So we're doing the task itself who's setting that to as TR dot.

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So this here is a special string glass and steel and inside the pants parameters here.

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We've caught inside the parentheses the self the task plus these SDR and then the number as Cha is a

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special string function class.

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Okay.

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And here again we're using the user dot without using the Self Variable dot the user in how we are setting

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that to this self dot task.

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So this is for the button click methods when they click on the button it will kick off this logic inside

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this code here.

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So take note that this is t r all we have use is a python built in string class.

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This is string class which is a built in function.

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Sorry built in class in Python it's a built in class called S T R string built in string class chord

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s t o I've created on another function here called calculate task again a past in a self variable here.

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And this function I've also attached some error handling Python allows you to implement arrows add exceptions

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to be handled by a program who allows your programs to handle arrows.

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An exception in order to do that you need to use a try and the accept statement.

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So here is my try statement and this is what I specified and here is the statement for my except so

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this try and accept there to handle any errors in the application.

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So basically what this is doing here.

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This function here any data that is passed into that variable we get is going to be the.

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Are you going to be any input so it's taking the input is getting the input from the user and then passing

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it into this variable here and it'll catch any errors here.

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Using this try.

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So if the answer if the answer evaluates 2 equals 2 that a tool to display it does not.

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If there is an error the error will be captured.

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Okay so this here is used to display the text of the answer.

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This will this also self-taught answer we display and the task has been imported.

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And here it's a syntax that will capture any invalid syntax you enter or any error messages to be captured.

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I've added two other functions here.

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This one here called display text and passed it.

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The self and then the value that the user inputs.

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So again this is what it will do.

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You take in the input from the user and if you decide to delete the little entry these are the parameters

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it would take.

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And if you're inserting it.

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This is a code that will handle the insert.

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Again this is a function.

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This here this function is responsible for displaying the text.

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This function here is responsible for clearing the display.

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OK so any input you enter here you can clear it using this piece of code there.

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So here and the bottom here whether this here.

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So we sat in the calculator so equals to this TKD method which we specified earlier on the T.K. route.

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So we are here both with this title.

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We using that to set the title for the calculator.

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And this is what we'll call it.

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Okay.

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This T.K. here is the route.

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So we're setting up the route of the application will be the calculator and app.

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The app here is refers to the application name.

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This is the name of the application.

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It's called calculator this here you use that to make the window a fixed window so the window cannot

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be resized.

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OK so hands up setting the height to force so you cannot resize the window of the calculator.

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Because of this line of code here and this is the main loop of the calculator.

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This is the event loop.

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This is what keeps the calculator running on to you exit the calculator.

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So that should be it.

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I'm presuming a click save.

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So let's do a quick review of our code.

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Make sure the code is also formatted properly.

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If your code is not formatted properly and you try to run it it can cause syntax errors and the editor

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will complain.

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So make sure you've got it structured the way I've structured might have also added some comments here.

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So anything you see here in green here these are comments.

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When you run the application the comments are ignored.

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OK.

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So these are comments.

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And also this here is a comment.

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Anyway you see the hash symbol is also a comment.

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OK so these are comments.

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It just helps give you a description of what we've done here.

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So this tells you here that this is the main class for the calculator.

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It tells you Here we are the initialize in the frame here.

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We're creating all the buttons for the calculator here.

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The user input we store in them as an entry widget.

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Here is the button for value.

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Number seven in here we've got value.

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Number eight.

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So these are our comments.

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Anything it's easy a pound sign is a comment.

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And so on so I've commented out just put a comment before each line.

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So you know what they do.

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OK.

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So make sure your code is formatted this way.

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In here there is a format option to endangered code.

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See if you notice knowing that properly.

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Make sure you do that so that the editor doesn't complaints you notice within the functions you see

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where the function is created and then the other actions the logic inside the function.

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There's indentation you can see that even with a class you can see the class the indentation from the

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class and the methods.

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If I scroll down you can see the indentation also.

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Okay.

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Here eyes all indented or the logic.

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It's indented underneath the respective methods.

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OK.

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So make sure is horse all sorted and structured in this way.

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So once you've done that you just click and save and let's try and run the application so click Run

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and to run module hopefully.

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Yep.

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Okay that's good.

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So this is the application here.

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Let's see if we can do some calculation.

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So that's eight times eight 64.

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We'll clear that nine plus nine 18 will clear that five fifty six minus eight.

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We'll clear that so all the one of we know use.

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Yes to a division we do hate to divide by six.

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Okay.

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Clear that nine divide by three.

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Can I that.

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So we've got all the buttons and the functionality working properly.

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So this concludes the series on creating a calculator with Python.

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Thank you for watching and bye for now.