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All right, let's play a little game, can you guess what the output of this program is going to be?

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I have over here equals one.

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Then we create a function called confusion where we have a equals to five and we return a my question

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is, when we print A and when we print confusion, what do you expect to happen here?

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Take a second to figure out pause if you need to, and let's find out.

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One in five.

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Is that what you expected?

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Let's go line by line.

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First, we assign value of one to variable A, we then create a function called confusion and Python

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interpreter is going to say, all right, confusion function, I know what it is.

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I'm going to put it in memory.

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When you need to use me, just let me know.

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And then it's going to go to line eight and line eight is going to say, hey, print a what's a..

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Well, the only time that I've seen A is right here, a equals one.

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So going to memory what say equals one.

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But then when I run confusion like this.

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I'm going to say, hey, A is going to equal to five and now we return, which is five.

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OK, what if I change the order of this?

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What if I go like this?

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What will happen?

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If I click, run.

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Is that what you expected?

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Once again, we have a close one, then we define the function and then we print confusion.

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Now, confusion here is going to assign a equal to five and then return A, but why didn't this change?

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Why is A still equal to one by the time we get here?

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And this is because of scope, right?

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What the Python interpreter does is when it runs the confusion function, it's going to say, hey,

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A is going to equal to five, but I'm creating a variable here called A in my own universe.

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I don't know anything about a equals one here.

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I have my own universe and after we run this function then, well, we're done.

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We've returned the function and it's completely gone.

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But we never left the universe into the global scope.

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So there's a set of rules that the Python interpreter goes through to check a variable and the rules

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are this.

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First, it's going to check with the local.

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So start with local and what we call is a local scope.

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A local scope is a scope that's part of this local function.

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So A is a local scope.

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It's going to check there.

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Hey, do I know the variable?

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A Well, yeah.

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When I return A, I have a variable defined here, so it starts there.

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But let's say a wasn't there.

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Let's say I remove and I click run here.

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I get both once, because the second rule is if there's nothing in the local variable or local scope,

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then number two, is there a parent local school?

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In our case, what's the parent of dysfunction?

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Well, it's the global scope, but we can also do another function.

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Let's say parent and parent is a parent of the confusion function.

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And in here, let's say a equals to 10.

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Now, in here, we'll return.

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Confusion just so we can use it again and actually run it.

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So let's call parent.

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And click run.

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All right, let's go through this so it's not too confusing.

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We have their parent function that gets called.

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So when we call that we assign a equals to ten and then we also create a new function, confusion.

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And then finally we return confusion and actually run it.

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So we're going to return A and then in here print whatever the value of A is, which is 10.

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And why is that?

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Well, because we first start with the local scope.

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Hey, this confusion know what A is?

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No, I don't have it in my local scope, OK, does my parent local scope have it?

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So it's going to go up a level and say, hey, does parent function nowadays?

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Yep, I have a close to 10.

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So it's going to print that the third rule or the third order is global.

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And global is what we call the indentation of nothing, it's this file, right, whatever the file has

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that is global in our case, if A equals to ten doesn't exist here, there's no local, there's no parent

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local.

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And I click run.

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It checks the global scope.

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And then finally, there's one other rule, and this is number four, and it's a tricky one, and this

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is what we call built in Python.

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Or built in python functions.

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So Python comes with predefined functions such as well, the some that we've talked about before.

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This some, let's say, just give it five.

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Is going to check or actually let's not give it anything, let's just do some here.

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When I run this.

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I get built in function some.

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Now, how did he know what this was, what this variable at the end of the day was?

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Well, it because it said, hey, do I have some inside of this universe?

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No, I don't.

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OK, do I have some in my parent scope?

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No, I don't.

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OK, do I have a sum in global?

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No, there's nothing some in here.

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And then the final thing it's going to check is, hey, is some some sort of a built in python function.

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Yep.

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Python actually gives us some so you can use it so it doesn't air out.

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And this is the scope rules that the Python interpreter falls very, very cool.

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There's still a few more things that we need to learn.

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So I'll see you in the next video.