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Great, you can now create functions, call them and

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add parameters to make them more dynamic. And now

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what you can also do is to make a function return

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a value. Okay, so this functions, say_hello is

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just a function that does an action, it doesn't

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return anything. Now I'm going to create a new

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function. So as you can see, when you just press

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enter here, I still have the indentation. So what

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I'm going to do, I'm going to remove that

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indentation, and do def again. So let's say I'm

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going to create a function double_number, and say

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a just number. So you can create as many

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functions as you want, you just need to put them

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one after the other. Okay, so now I'm going to

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create a function with one parameter, and the name

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of the function is double_number. And I simply want

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to return the double for this number. So I'm

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still going to compute the result, which is the

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double of that number. So I'm going to create a

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variable result is equal to number times two. And

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then what I'm going to do, I'm going to use the

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return statement, return result. So what this

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function will do when it's called? So first it is

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going to receive a parameter number, it's going to

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compute the double of this number and return the

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result. So when you call the function, you can get

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the double of the number you sent. Just before we

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continue, one thing I'm going to do here is that

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so we create a variable and we just return that

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value. So basically, we are not going to use that

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we only return that variable. So what we can do

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instead of result is equal to number times two and

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return result, we can just return number times

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two and remove that. So this is going to return

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directly the correct value. And now well, I can

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call this function, so I'm just going to put a

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comment here. Okay, so we don't call those so this

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is not a problem, you could call this and call

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this, that's not a problem. Here, I just want to

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call that function and not this one. So we just

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have less lines, okay, in the output. So what I

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can do, I can do double number, I can use the auto

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completion, with let's say, three, okay. And I'm

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going, of course, to store that. So let's say

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number is equal to double_number(3), and then

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print number. So when you create a function that

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returns something with the return statement, you

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can, when you call the function, you can actually

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assign the value, you get here to a variable. And

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then you can print of course, the variable, or you

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can do whatever you want with the variable. So I

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just ran the program, and you can see here we have six, so

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the double of three is six, so the number variable

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here contains the value six. Alright, so you can

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see two types of functions here. So those who are

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just going to do an action and don't return

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anything, and those who compute or maybe get a

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value from some way and then return that value.

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Now that you can return any kind of value you

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want, here, I return an integer number, but you

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can return a float, a Boolean, string, list of

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whatever you want, well just return what you want

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from a function. But just make sure that when you

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call the function, you actually know what kind of

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data type you're going to get. Okay, and one thing

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you can also do is you can call a function inside

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another function. And those you can really make

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functions as building blocks that allow you to

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create even more building blocks. Let's see that

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with an example. def print_double_number. So

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we've number and I'm going to do results is equal

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to double_number of the number we get here,

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and then print, result or maybe make it better.

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So Double of plus, the number cast it as a

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string plus is and plus the result also casted

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as a string. So when you call this function, what

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it's going to do is, going to call the double_number function.

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Okay, so from the function you

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call another function, and you can see this

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parameter I got here, I'm going to pass it also to

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the double_number function. And then I can print

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some stuff with the parameter and the result I

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got. And I'm going to call this print_double_number.

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I'm going to remove that.

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I'm going to remove that and I'm simply going to

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run. And you can see double of three is six.

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Okay. It's all happening in that function. So here

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you have a function that just does an action and

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that's it. Here a function that returns a number.

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And here a function that does an action but inside

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you actually call another function and you can

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create another function that is going to call that

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one, etc, etc.