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Now is the time to start working with functions. A

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function is a reusable block of code that you can

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reuse later in your program as many times as you

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want. So why do you need functions? Well, this

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will help you create building blocks in your

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program that you can use and reuse on top of each

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other, so you can increase the complexity of the

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application, without increasing the complexity of

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your code. Your code will stay clean, and easy to

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modify. And instead of giving you many theoretical

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explanations, let's dive in and write our first

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function. Okay, I'm going to remove all of that,

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I'm going to create a function. So to write a

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function, you first need to write the def, def and

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then space, and then the name of the function.

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Let's say we want to function that says hello. So

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I'm going to write say_hello. That is the name of

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the function. After the name of the function, you

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need to open and close parentheses, and then add a

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colon. After this, you can press enter, and as

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you can see, the marker here doesn't, the cursor

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doesn't come back to here. It come back to here

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with, as you can see here, 1234 new spaces, which

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is called the indentation, okay. So you're going

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to write everything under this function with an

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indentation of four spaces. So I can write any

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instruction I want. So for example, print("Hello").

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Okay, that's a very basic function that just says

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Hello. So def,name of the function. So again,

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what you can do, if you want to add multiple

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words, you can add an underscore, and then parenthesis colon,

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and everything you write inside the

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function will be with an indentation. Now, if I

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run that code, let's run the main, you can see,

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well, we have nothing. Why is that? Because we

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have just created a function, okay, we didn't call

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the function, okay. If you just create, if you

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just define a function like this, it is not going to

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do anything. What you need to do in your code is

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to call the function, and to call the function, you

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just write the name of the function, okay, with

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the parentheses. And then you can run the

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again, and you can see Hello. So the good thing

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about a function is that you can actually call it

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multiple times. So I can just copy this and paste

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it three times. And it's going to call the

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function three times. You can see Hello, Hello,

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Hello. So of course, make sure you define the

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function before you call it okay, otherwise,

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you're going to get an error. And then as you can

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see here, everything that is indented will be

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under the function. So let's say I write print,

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let's say I write test, okay. I can run again and you can

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see Hello, test, Hello, test, Hello, test. So if I

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continue to add lines after this one, but with an

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indentation of four spaces, it's going to be under

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the function. When I go back to the default

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indentation of zero spaces, we are back to the

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main program and then so we can call the function

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directly like this.