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Instructor: Welcome back.

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Let's try and answer some questions that you may have.

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For example, what about parameters?

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If I do parameter, let's say b here,

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what is this parameter when I use b like this?

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So let's say print b.

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And in here, I'll run confusion,

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with let's say b number 300.

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If I run this,

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this works.

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And that is because b, the parameter,

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is part of the local scope.

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That is, it's part of this.

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So parameters are considered local variables.

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We're able to use it inside of the function,

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but we can't use it outside of those functions.

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Technically, when we define the function

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we let the interpreter know,

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hey b is going to be a local variable.

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Okay, what about this?

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What if we have this, a,

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but I wanna make sure inside of my function

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that I'm actually referring to the global a.

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Is there a way for us to just use this value

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without creating a new variable?

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Well, let's use a better example for this.

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Let's say I wanted to create a counter.

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So we'll have total equals to zero,

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and then in here

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I'm going to say define count.

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And this function is going to say total,

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plus equals one,

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so we're gonna add every single time.

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When we add count

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it's going to increment zero by one

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and then one by one, so on and so forth.

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So we're going to return

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total at the end of this.

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Okay, so if I run here, print,

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count,

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let's see what happens.

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I'm going to hit run and I get an error.

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Local variable total,

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referenced before assignment

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and that is because well count doesn't know about total.

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You're trying to use total

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but we haven't assigned anything yet.

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But we want the total from the outside world to run

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because if I just do total equals zero here

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and I run count,

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that's great, I get one.

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But what if I wanted to run count multiple times?

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What if I wanted to run count

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let's say three times

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so that the count total will be three.

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So let's do print on the last one here,

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and I click run.

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I still get one because every time we run the function

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we reset the total to zero.

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That's not very useful, is it?

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So one way that we can fix this

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is using what we call the global keyword in Python.

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And global says,

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use the global total,

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if it exists in here.

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So that instead of having to create a new variable

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I can use the global variable total.

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Check this out.

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Well, I get an invalid syntax,

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and that is because we first have to say

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global total is gonna be used in here,

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and then we can say total plus equals one.

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If I run this,

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hey look at that, we have a proper counter.

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So global is a way for us to access this global variable.

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However, I argue that this is actually

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not a good way of doing things

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because it can get really confusing

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when you start adding globals,

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and all these different universes

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are accessing each other's variables.

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A better way of doing this

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is something called dependency injection.

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And this is a simplified version of it.

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But the idea is that instead of accessing variables

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outside of the function like this,

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which can get really really complicated as files

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get bigger and bigger,

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is to do instead this,

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total like this.

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We create a parameter and then we pass in

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that parameter or argument in here.

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But as you can see, it's still one

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because by the time we print the third total

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well this never changes.

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This is a global zero.

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So instead we can do something like this.

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We can say count total,

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of which we're going to count again,

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and then count again.

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If I run this,

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I get three, and I know what you're thinking.

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This is completely insane.

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It looks confusing.

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Look at all these brackets,

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but let me show you what we've actually done.

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We're able to detach the dependency

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or the effect that this count function had

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on the outside global scope,

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and instead just focus on its health.

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All we needed to do was say,

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hey, I want you to give a count with total of zero.

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And then after that this is going to evaluate two one

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and then we do count total of one plus one

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is going to equal to two,

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and then count two plus one is going to equal to three.

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And this way we're able to still do our count

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without having to use that global keyword

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which I would argue is nicer.

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Mind you, if this is your first time seeing this,

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it can get a little bit tricky,

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but at least this way you know that there's

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different ways of doing things.

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One other word I wanna show you

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is something called non-local.

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But for that one, let's take a break

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and I'll see you in the next video.