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Hey guys, welcome to this lesson on

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how the input() function works in Auditorium.

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Now, this is an important lesson

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because inputs actually work a little bit differently in

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Auditorium compared to what you have seen so far elsewhere.

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Now the first thing you'll notice is that in exercises

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that require an input,

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the Input pane will show up on the bottom left.

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And here occasionally I might start you off

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with some example inputs,

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but if you see the Input pane, you can always delete

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what I've written in there and replace it with your own,

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or write multiple lines of inputs,

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but how does it work exactly in Auditorium?

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Well, it's mostly used for us to be able to test your code,

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to be able to see that you are writing the correct code

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and to make sure that you are on the right track.

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So let's take a look at

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how inputs work in a little bit more detail.

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Take a look at the code that I've written here, print,

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and then the input function,

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and then closing the print statement.

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Go ahead and run this code

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and see what gets printed in the Output area.

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Can you see where it comes from in the Input pane?

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Now notice how I've added two more of these lines of code.

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Now, if you go ahead

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and run this code now as it is,

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you should see all three names in the Input area printed

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into the Output area.

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So the way that input() functions work in Auditorium is

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that you can go line by line from top

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to bottom in the Input area,

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and as long as you write the input function,

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so the word, "input" plus the opening

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and closing parentheses, it will look in the Input area

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and pick out each one line by line.

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But now we have an interesting problem,

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what if I have four of these lines of code to try

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and pull in four inputs?

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While, if you take a look in the Input area,

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there are clearly only three lines of inputs.

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Jane, Ben, and Tom, there is no fourth input line.

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So what happens here?

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Well, if you go ahead and run this code,

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you will see an error.

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And this is where you are trying to pull in an input

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that doesn't exist in the Input pane.

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So if you familiarize yourself with these errors,

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then if it does happen in the future,

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you'll know exactly what's going on.

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So when you do see that end of line, then you'll know that,

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"Oh, maybe I've added one too many inputs,

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and it doesn't actually exist in the Input pane."

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Now the final thing I want

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to mention is unlike previously when you've been writing

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Python for your projects, when you use the input prompt,

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because we don't need the prompt in order to get hold

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of the input, this prompt actually goes into the output next

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to the input name.

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So when you run the code here, as you see right now,

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you'll see the words, "What is your name?"

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And then immediately the first line of the input.

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Now this is not what we want

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to do on the Auditorium coding exercises

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because we're testing your outputs to make sure

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that you're getting the right results from your code.

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So in all cases, when you are using the input() in Auditorium,

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I recommend to use it without any prompt text.

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So simply the keyword input, an open parentheses

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and a closing parentheses,

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and that entire block will be replaced

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by whichever Input you have in the input pane.

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Now take a look at this Demo coding exercise.

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Now without changing any of the code in main.py,

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go ahead and simply click on the SUBMIT button

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and run all of the tests that we've prepared for this exercise.

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Now, one thing you'll notice is

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that the code should pass all

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of the tests in the Evaluation pane.

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But notice in the Input area, you only see two numbers.

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So the code here on Line 4 multiplies num1,

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which comes from the first line of the Input area,

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by num2, which comes from the second line

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of the Input area.

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Now, in order for us to be able to test your code

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to make sure that you're doing the right things,

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we will add hidden inputs and hidden tests.

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So when you run the code,

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you will see other tests being run in addition to the input

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of 2*3.

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This way we can ensure that your code is actually code

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and it's doing what it's supposed to do,

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and it covers all of the corner and edge cases.

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Now notice what happens if a student completes the exercise

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without actually completing the objectives of

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what we're testing them on.

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So in this case, we're pulling-in num1 from Line 1

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of our Input, which is 2,

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and we're pulling-in num2, which is 3,

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and then we simply printed 6 on Line 4,

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'cause I know very easily that 2*3 is 6.

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Now, however, if you go ahead

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and click on the SUBMIT button without, again, changing any

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of the code in the Demo, then you'll see that one

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of the test pass, but the other one fails.

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And this is because

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that the first test case is 2*3,

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which does equal 6,

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so your output from your code is 6,

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and the expected output is also 6.

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So that works just fine.

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Now, however, in the second test case, this doesn't pass

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because we're printing the output 6,

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whereas we've got some hidden inputs testing your code

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against the inputs of 5 and 5.

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5*5 is 25, and 6 does not equal 25

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and that's why the second test fails.

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Now you might think to yourself, well, how can I write code

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that works for all of these test cases?

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Well, you would have to write actual code like

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what you saw in the previous slide, which takes in any input

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and doesn't care what number it is,

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and simply multiplies the first number by the second number.

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So head back over there if you're confused,

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and see if you can fix this slide so

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that all the test cases pass.

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Now, try it yourself, try pulling in some

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of the inputs from the Input area.

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So look at the Input pane at the bottom left,

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go ahead and change the values that are in there,

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you can add as many lines of input as you want

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and then try writing some code in main.py in order

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to print the different lines of input into the Output area.

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If you get stuck, look back at the previous slides to see

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how you can pull in the input using the input function.

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Now in the final coding exercise of this lesson, I want you

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to figure out how to pull in the inputs

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and calculate the number of letters in the names

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that I put into the input.

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Now just before we do that, I want to show you

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how you can actually get hold of the number

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of letters from a piece of string in Python.

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So the function in Python is called len(), which stands

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for length, and you can use len

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and then a set of parentheses,

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and then inside the parentheses add some text such as

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what you see here on Line 1.

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And when you print the result of that,

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you will see the number of letters in

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that text being calculated.

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Go ahead and hit RUN CODE and see this for yourself.

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So now you're finally ready

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to tackle the final coding exercise of this lesson.

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So take a look through the instructions, the hints,

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and see what we're expecting you to get as an output.

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So the task for today is

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to pull in the text from the input area.

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There will only be one line of inputs,

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and this will be a name.

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So you can see in the starting example,

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I put my name in there,

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and your job is to write some code in main.py in order

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to print out the number of letters in the name

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that's put in the input.

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Now of course, remember what I mentioned

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before, when we're testing your code, we're going

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to pass your code with inputs

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that I have hidden away.

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So when you submit the code, when you think you are ready,

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you'll see different inputs being passed through main.py

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and your code has to work for all of them.

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So make sure you're writing code

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and you're not just simply calculating it using your head,

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and that way you'll be able to pass all

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of the tests in the Evaluation pane.

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So give this a go

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and if you get stuck, there's always the next slide

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where I'll go through the code solution,

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but also you can head back a few more slides previously

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and see if you can figure out the solution yourself.

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Now we're going to break down the solution into three

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distinct parts,

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and the first part is the input() function.

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The input() function can bring in the value

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that's in the Input pane.

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So that's the first part we need to get hold of.

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Now that we've gotten hold of the text on the first line

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of the Input pane, then we need to put it

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inside the len() function.

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So as I showed you earlier,

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the len() function can take any piece of text

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and tell you how many characters

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or how many letters are in that piece of text.

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So in this case, we're simply inserting

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what we got from the Input into the len() function in order

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to perform this functionality

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and let us know how many letters are in the input text.

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Now, of course, when you saw it before you simply saw len,

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and then in the parentheses we added in plain text,

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but in this case, we're writing our code

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to perform things automatically

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and it has to work for all of the different inputs, not just

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for the word Bertrand.

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So in this case, we're taking the input

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and putting it inside the len() function so

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that it'll work even if we switch out the input

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with any other name.

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Now, the final part is to put all of

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that into the print() statement.

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So remember, inputs go into the part

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between the parentheses.

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So now we have a complete program

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where we first take the input,

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we put it into the len() function, we calculate the length

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of the string in the input,

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and then we put that into the print() statement

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and we print it out into the Output area.

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So each of these functions had a distinct role,

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and by putting in them one into the other, we end up

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with the result we want.

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Now, if you got stuck

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or if you had any differences in your code, feel free

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to go back to the previous slide and update it

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now. As long as you understand exactly what's going on here

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because there's several steps involved, then I'm happy

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that you have mastered the art of the input() function.