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There is one important thing I want to talk to you

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about before we continue, and this is the scope of

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a variable. The scope refers to where a variable

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exists and where it is available. Depending on

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where you create a variable, it may or may not be

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available to other parts of the program. And to

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explain this, I'm going to start with an example.

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So we are going to continue with our code here, we

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have so, call to print_double_number(3). And

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what I'm going to do after, I'm going to do print(result).

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I'm going to print the result variable

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that we have created here. Okay, so as you can

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see, as a warning, it's already red, so let's

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see what it does. And we have an error here. name

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.result' is not defined. Why is that? We create a

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variable result, and then we can't use it, it's

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not defined. This is because of the scope. So from

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what you have seen before, if you create a

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variable, let's say create a variable a is equal

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to two, then I can use the variable a, after I've

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created it. So after line 11, I can use the

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variable a as many times as I want. But when you

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create a variable inside a function like here,

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well, this variable will not be available from

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outside of the function, as you can see here, with

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this error. The variable that you create outside of a

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function, for example, here, a is equal to two,

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this is a global variable in the global scope,

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okay. And the variable that you create inside the

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function is what we call a local variable, which

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only exists inside this local scope of the

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function. So knowing this can avoid you a lot of

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errors in the future, okay. When you create the

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global variable, you can use it everywhere after

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you create it. But when you create variables

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inside functions, well, the variable can only be

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used inside the function. And this is also what's

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happening with parameters, okay. When you have

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parameters, any parameter you have here, you will

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be able to use it inside the function, okay, but

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this basically, for every parameter, it's going to

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create a new local variable inside the function.

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So here if I say, Hello, you have two local

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variable user_name and user_age. For double_number,

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you have a local variable, named number.

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And for print_double_number, you also have the

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local variable named number. And as you can see

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here, because the scope of this, scope of this, and

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the scope of this are different, here this is not

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a problem to use number twice, okay. Because this

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is actually not the same as this, this number is a

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local variable inside this function. And this

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number is another local variables inside this

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function. So you can have two variables with the

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same name in different scopes, and they are going

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to be different variables. Alright, so very

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important thing to ask yourself when you create a

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new variable, where does these variables exist.

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And in the current scope, I'm writing code right

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now, can I access this variable? Okay. If you want

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to access the user_age, well, you can only access

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the user_age inside the function say_hello. So if

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you write code here, yes, I can access user_age.

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Here, no, I can't access user_age and outside of the

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function neither and very basically, but when you

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create a new function, you create the new local

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scope with new local variables. Alright, so

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knowing this will help you understand some erros

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when you get started. And later on, it will help

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you also to avoid those errors.