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Remember, you should be careful with variables that have global scope,

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but don't believe the people who tell you that you should never use global

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scope. Global scope can be incredibly useful

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especially when you're defining constants. Global constants

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are variables which you define

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and you're never planning on changing it ever again. It's just something like,

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for example, the value of pi, right?

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You want to look it up once and you want to put it into your code and you never

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want to look it up ever again.

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And every other time you want to use it, say inside of a function, then all you

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want to do is just tap into that value of pi.

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So usually, in order to differentiate these constants

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which you're pretty much never going to change from the variables

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which you are likely to change,

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the naming convention in Python is to turn it into all uppercase.

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For example,

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if you had PI or you had a URL that you needed to use,

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or you have some sort of Twitter handle,

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then these are all going to be uppercased, separated with underscores.

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What this means is that later on in your function and you want to use one of

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these global constants, as soon as you type it,

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you can see it's the uppercase and you know

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to remind yourself to not modify this inside your code.

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Now that we've talked a little bit about scope,

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it's time to put your knowledge into action. Head over to the next lesson

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and I've got a quiz that will test your understanding.

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So, for all of that and more, I'll see you there.