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Hey, in today's code experiments, you will learn some tricks about modules.

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That will give you a better understanding of how Python works.

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The experiment we want to run is pretty straightforward.

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I want you to go to functions that P where we have defined our functions.

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And below the functions somewhere down here, just print something like Hello from.

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Functions.

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So this has to be outside of the function definitions.

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You see, it's an indented.

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Then I'd like you to go to Maine.

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That PI where we import functions that model and run Maine, that pie.

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Then in the command line here in the output, what you'll see is helo from functions.

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So with this experiment, what I wanted to show you is that when you import a module from another module

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and then you run the module where that module is imported.

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So when you run main that p y in this script is executed when that script is imported, So the module

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is executed at this point in here.

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To illustrate it with another example, I'll stop this and go back to functions and introduce an error

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here.

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Instead of printing out the string, I'll print out something like x.

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X is not defined, so this will cause an error.

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So now I want to go back to Main that p y or run again.

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And this is what we get so of error.

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First started.

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At this line, line two in main p y.

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So that is this line in here.

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So this line actually tries to execute functions that p one.

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So it tries to execute that.

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And then if we trace the error, it says that in line 16 in file functions that p y line 16 is this

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one.

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We have a name error X is not defined.

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So why did I introduce this error?

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Well, that was another way to demonstrate that when.

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An import operation happens.

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It executes functions that P or whatever file you are importing.

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This is important to know because.

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Sometimes you may want that certain code is only executed, for example.

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Hello.

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You might want that.

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This code is only executed when this script is executed directly.

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As in.

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Run functions.

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So we get Halo here, right?

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And so maybe you don't want to execute that halo when you run main that pie, but still you get that

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executed.

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So how do you avoid executing that?

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Line.

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When you import, there is a way for to do that, actually.

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That is to put this line into a conditional block.

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But first of all, why would you want to execute this only when you imposed that function?

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Well, maybe you just want to.

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Print out.

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Get to dos.

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Right.

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You want to test the function output, so you get that, but you don't want to see that.

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When you run Maine.

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But again, Maine, that pie will also return that output of the function called Get to deuce.

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So we only want to to see that when we execute this code directly, maybe we are testing these functions

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out.

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So we just want to, to work on these functions that p y.

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So the solution, as I told you, is to have a conditional block.

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And you say if underscore, underscore, name, underscore, underscore is equal.

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So double assignment operator is equal to quotes, open and close.

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Underscore, underscore, main, underscore, underscore.

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And then you put here a column and then these should be indented under that.

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Let me make a break line.

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So that's the if conditional.

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Now if I run the script functions that p y again I get that executed and that as well as you see the

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output in here and there.

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But if I execute main that P now you see that.

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These two lines were not executed.

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We don't have that code in here.

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These are executed.

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So the functions are defined when we import functions.

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And these functions definitions are available here.

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So everything that is outside that if conditional.

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Such as this print function is executed.

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If I execute main that we will see that we get that output because it's outside of that if conditional

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block.

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Now what is this?

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If conditional block, what does it do actually?

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Well, we have a variable here.

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This is a variable.

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But it is a variable which is defined hideously by Python and its value.

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And I'll show you what value this name variable has.

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So let me print that here.

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So print name and I'll execute this script functions.

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That's p y and that is the value of name.

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This is a string.

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So if you check the type.

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Of the value of the variable name, you'll see that it's a string and its value is.

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Maine.

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So that is a string.

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But its value is main only when we execute functions that p directly run functions.

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If you execute execute main that p y you'll see that the value of name is functions.

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So we get that printed out from that line.

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So to sum it up, when you run Maine, that's p Y and Maine does P runs functions that p y through that

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import statement.

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Then the value of name is the name of that file functions in this case.

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But when you run functions that p directly.

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The value of that variable is underscore, underscore, main, underscore, underscore.

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And that allows us to have this condition here.

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So if name is equal to that string.

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I mean, that means somebody is running this script directly, and that's somebody which is us.

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That somebody wants these lines to be executed.

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Otherwise, if I'm being imported, the file says, then I will not execute this because my name is

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not Main is something else.

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So that is the distinction we can make to control what we execute when the file is run directly and

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what we execute when the file is run indirectly through this import statement.

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This can have practical uses in certain scenarios, especially when you build web applications.

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So in that case, you might want to use that to have different outputs when you test the code and so

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on.

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So that's something you should know and I hope it makes sense.

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You'll see this if name is equal to main in other people's code, and this is actually one of the most

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asked questions on the internet about Python.

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People ask what is if name is equal to main?

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I hope this makes sense to you and you don't have the same question later on.

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Thanks a lot.

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See you later.