Original subtitles

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Coming back to our Repl.it,

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the Day 1 printing repl that you should have from previously,

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I want to talk about a different function.

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So we've seen the print function and all the things that we can do to strings

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and use the print function and debug it.

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But what if we wanted to be able to enter some data?

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So if we wanted to say,

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ask the user 'what is your name?' And we run this code,

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you can see that being printed,

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but there's no way for the user on this side to be able to give our code some

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data to work with. In order to do that,

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instead of using the print function,

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we're going to use a different function and it's called the input function.

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And notice how as I'm typing,

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code intelligence is already giving me some suggestions because it thinks it

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knows what I might want and it's right.

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So this is what the input function looks like. This is the name of the function.

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And again, it's followed by some parentheses. Inside the parentheses

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is the prompt that I'm going to give the user.

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So when I run this code, it will say, what is your name?

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And then the cursor will stay at the end of this line because it's expecting

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some sort of input. If I give it my name, Angela and I hit enter,

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then this piece of data has now been passed back into my code and it now

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replaces this part of the code.

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So I'm passing data from over here,

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back to over here where I can use it in my code.

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Now notice the difference here. It looks quite similar.

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When we run print, you can see it says what is your name?

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and then the code execution ends and we know it ends because it's showing us

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this little orange arrow.

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But notice when I run input instead,

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I don't see the orange arrow.

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My program is actually paused right now in order for the user to provide an

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input and it's only when I've given the input and hit enter

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does the program end.

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The input function looks pretty much identical to the print function,

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but instead of the word print,

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it's just got the word input. And inside the parentheses,

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instead of adding what text will be printed,

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we're adding the prompt for the user to give them a hint as to what kind of data

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we want. And then when you run this code, it will print out the prompt,

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but then there will be a cursor. In some places you'll see it like a flashing

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cursor, other places,

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it'll just be a solid cursor ready for the user to type in some piece of data.

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So what can we do with this data? Well,

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we can use it inside our code.

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Remember how I said once this line of code executes and I've entered Angela as

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the response to this input,

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then this part of the code gets replaced by whatever it is that the user typed

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in. So in this case it becomes Angela.

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And what I can do with it is let's say I wanted to print something like,

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hello Angela. Well,

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then I can simply write Hello + input and then I'm going to close it off

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with another set of brackets.

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So I'm going to change my layout instead of side by side,

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I'm going to change it to stacked.

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And this means that I've got my code at the top and my console at the bottom.

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This way my line can go a little bit longer without it rapping.

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Notice what's happening here.

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This is the input function that I showed you earlier on and this is a print

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statement.

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So we've got this nested inside the other. And now when I run my code,

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what happens is it asked me what is your name?

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So I'll write my name and then when I hit enter,

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this part is replaced by Angela and it gets concatenated to the word hello and

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the entire thing gets printed out down here.

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If you find this line of code difficult to understand and to wrap your head

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around,

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then I recommend heading over to a website called thonny.org and downloading an

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application called Thonny. It's completely free and it's available for Windows,

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Mac, and Linux. And once you've installed this application,

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you can go ahead and paste your line of code here and click on this little debug

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symbol. And then we can click on this button,

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which is called the step into button to step into the execution of this line of

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code

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to see how the computer is evaluating this code here step by step.

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So you'll see the first thing it tries to do is it will try to run this print

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statement. It looks inside, these parentheses to see what it needs to print.

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So the first thing is this, Hello,

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and it turns that into a string and then it looks at the next thing after the

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plus sign to see what it should turn this into.

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And this of course is the input function. So as I continue stepping into it,

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it's actually going to execute it.

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So it's going to run this input function and show the prompt, what is your name?

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So that's what shows up down here.

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And now if I enter a value in here and hit enter,

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then that value that I put right there replaces that previous input function

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and is now held inside the print statement.

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So if I continue stepping through this code then you'll see it concatenates all of

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the pieces together, and finally it just ends up with a simple print

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Hello Angela! And if I continue stepping into it,

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you'll see that line of code executed until there are no more instructions left.

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So if you prefer seeing your code, um,

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run like this step by step so that you can see what's going on,

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then I recommend giving this a go.

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But because of how easy it is to share these Repl.it code bases so that we're

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working from the same place, I recommend to do most of your coding here

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and only if you get stuck to take a single line of code and paste it into Thonny

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to see how it's executed step-by-step. As you're learning to code,

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there's going to be new concepts covered.

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There's going to be things that take a little bit of thinking before you can

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understand it.

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So what a lot of programmers love to do is they like to comment in their code.

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Now,

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you might've seen this already throughout the coding exercises and the solutions

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I provided. But in Python,

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if you wanted a line of text to not be considered by the computer at all,

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all you have to do is add the hashtag or pound sign in front of your text and

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this turns it into a comment,

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so something that the computer will completely ignore.

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So in here you can write code as much as you like, um,

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but it won't be executed and when you click run,

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you'll see that this is completely ignored.

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What I recommend is whenever you come across a new concept in the course to make

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a comment above it so that you can explain to yourself what's actually going on

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in the line of code below. This way

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the next time you come across this line of code and you're not quite sure what's

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actually happening here,

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you can have a look at the notes that you've written for yourself in your own

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words and hopefully it'll re-jog your memory and make it much easier to

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comprehend what's going on.

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In addition to adding a pound sign manually,

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you can also highlight a line of code or simply have your cursor on a line of

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code and hold down command and forward slash if you're on Mac or control and

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forward slash if you're on Windows.

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And if you want to go back or undo your changes,

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it's simply command +z or control + z. All right,

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so in this lesson we learned about input function,

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we learned about putting functions inside other functions and being able to get

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user input from the console by using the input function.

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So now I've got a coding exercise for you in the next lesson,

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and if you've commented this line of code thoroughly and you fully understood

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how it works, then you'll be able to breeze through the next exercise.

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So for all of that and more, I'll see you there.