00:06Let's talk about functions.
00:09Function is repeatable block of code.
00:12So you can have some code, for example x is 3, y is 5, print x, print y, whatever.
00:21And now whenever you want to output that you would have to call those print functions,
00:24right?
00:26So, let's say you want to do that 10 times, you would have to copy those lines of code
00:32again, again, again, again, again, well you see where this is going.
00:38It would be just very inconvenient, especially if we have hundreds or thousands of lines of
00:42code to keep repeating those lines of code.
00:48So what programmers did a long, long time ago is to create functions.
00:52A function is one or more lines of repeatable code, so you can just see it as a function,
01:01can be any name, for example, show x, y.
01:07You write dev, Python knows that you're defining a function.
01:11You need those brackets and a colon at the end.
01:14Four spaces for everything that belongs to the function, and we'll say print x, print y.
01:20Now, the function wouldn't know about x and y now, so we need to pass that here, x, y.
01:27You can remove all of this, and say show x, y with whatever numbers you want, x and y.
01:34When we run it, you'll see it shows x and y.
01:40And whenever we want to repeat those lines of code, we just call the function again.
01:44So now you'll see it does it many times.
01:48Every time it jumps to this function, runs the code, goes back, jumps here again, goes
01:54here, does it again, and so on.
01:56So you can use functions to repeat code, and they can take parameters.
02:01This can be any parameters you want, so we can also, for example, write numbers here.
02:13And when you run it, you'll see it outputs those numbers.
02:17So functions are repeatable box of codes, in this case two lines.
02:20They can be hundreds of lines, it doesn't really matter, even one line is possible.
02:25And you can have different functions, for example, maybe you want to show some information.
02:30So show info, maybe name, job and city, then you can say print.
02:41Name is name, so you can output that.
02:48And we can say show info, with that information, let's say he's a programmer, from Peru.
03:06And now you'll see it calls the function.
03:11It seems we made a small error here.
03:13We need to have a colon here on the end, otherwise it won't run.
03:16So all functions should have a colon in the end.
03:19And you'll see it outputs that text, so whatever you pass to the function.
03:24And if you call it again, you can write your own variables in here.
03:29So let's say Alice is an airline pilot from Aruba.
03:39And you'll see it calls those, it calls that information, of course you can do it again.
03:47So show info, Bob is a builder from Belgium.
03:54See it runs those same lines of code, in this case one line of code, but of course you can
03:59have multiple, let's say you have multiple lines of code.
04:10And if you run it, you'll see it runs those lines of code, every time you call the function
04:15with the variables.
04:17Now this also works for lists, so for example if you have a list of people, let's say people,
04:26and there is Peter, Alice, Bob, then you can say for p in people, or let's make it a more
04:40explicit person, call the show info function, with the person's name.
04:46And you'll see it also needs the job and city, but for now we don't have that, so we can
04:51say
04:51it like this.
04:54We run it, and you'll see it calls the function for every item in the list.
05:02You'll see Peter here, it runs the function for Peter.
05:05Then it goes to Alice, so it does that for Alice, and runs the function, and finally we
05:12have Bob.
05:13So it calls the function show info, and it does it for Bob, that's why you'll see the
05:17output like this.
05:19Of course you can also do the same for job and city, you could have a list of jobs.
05:32And a list of cities, but perhaps you would want them to be together.
05:39So I would have a list in a list.
05:51So now we have lists inside lists.
06:08And instead of, we can still call it Peter, but now we have person zero, person one, and
06:15person two.
06:16Now that doesn't refer to another person, but to the position of their parameter.
06:22If you run it, you'll see now it outputs all of the information for every person.
06:27To make it more explicit, we can put some line here.
06:32So you'll see it calls the function for every item.
06:36So functions let you repeat code.
06:38You can run it, use it even with long lists in this case.
06:42It can be much more simple.
06:44For example, you can have a function sumab, which just turns a plus b, or sorry outputs
06:52a plus b, and show for example 10 plus 10, and you'll see.
07:01In this case, we're not calling the function sum, and you'll see it outputs 20.
07:09So you can have also like functions.
07:12If you have a variable in a function, like variable x, then that variable x only exists
07:21in those two lines of code here.
07:22So only within the four spaces.
07:24If we try to print x here, you'll see it throws an error.
07:30Even it shows already an underscore inside Visual Studio code.
07:33That's because x doesn't exist at this point.
07:35It only exists within a function.
07:37If you run it, you'll see an error.
07:39You'll see x is not defined.
07:41We defined it here.
07:42But when you define a function inside a function, it only exists within a function.
07:47So any variable you define inside here, that only exists within the block of code of the
07:55function.
07:55And that block of code is indicated by four spaces.
07:59If you want to keep the output of a function, you can say return x, and then store that output.
08:06So x is, and then the function name, and output it.
08:09If you run it, you'll see it outputs the data.
08:13So that's all about functions.
08:16Functions let you pass parameters.
08:18So the parameters you want.
08:28And you'll see, now we have a function with one parameter.
08:32So functions are just repeatable blocks of code.
08:35You can pass any variable.
08:36And if you want to store the output, you use the return statement.
08:40You can get the
08:40button to view all the elements.
08:42And now we are going to take reference to functions.
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