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Welcome back.

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Now that we've discussed
returning values from functions,

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we're going to build on this by learning
how to send values to functions.

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We've been using some pretty
simple examples so far.

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Our function that adds two plus two
together wasn't very interesting,

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even after we returned a value from it.

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You might be thinking I still don't
get why functions are so useful.

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Well, let's expand on this.

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Our 2 plus 2 function
would be a lot more useful

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if we could use it to add the number 2 to
any integer and we can totally do that.

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Just like functions can send values
back via a return, functions can receive

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values too and they can see, access and
use those values inside the function.

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This is all done by what’s called
passing an argument to a function.

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There are two parts to this.

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First, when we call a function,
we can send a value.

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Second, the function has to be written so
we can receive that value.

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Have you ever wondered about those
pesky parenthesis we have to

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add when defining or calling the function?

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Those parens are where the sending and
receiving of values takes place.

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Let's revisit our two plus two function.

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Okay, first, I'm gonna change its name.

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Instead of 2 + 2, I'll call it add_two.

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This new name makes more sense because
we're gonna modify this function so

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it now adds 2 to whatever
integer it receives.

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Now inside the parens,
I'm gonna create a variable.

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I'm gonna call it num.

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Right now num has no value, it won't be
assigned a value until the function is

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called and a value is passed but
we'll get to that in just one moment.

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Now that we've created
a variable inside the prints,

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this special kinda of variable is
known as a parameter by the way.

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We can use it inside of our function
just like any other local variable.

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That means we can change the body
of our function like this.

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What we've done here is rewrite our
function so that it can receive a value,

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which is stored in the parameter
variable called num.

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And then we can use that
value inside the function.

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So how do we send that
value to our function?

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Well, this happens when we call it.

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First we'll rate a regular function
call to the add_two function.

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To send a value,
we add it inside the parens.

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This value is called an argument.

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An argument can be any Python data type or
expression that evaluates to a value.

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This means you can pass in an integer,
a string, a function call, and

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even other Python data types that
you haven't learned about quite yet.

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In our case,
we're just gonna be passing an integer.

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Let's pass the number 5.

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Now, like we learned
earlier in this course,

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not much will be visible to us
if we run our program right now.

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To add some clarity to what's going on
behind the scenes, I'll add a print

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statement inside our function that prints
out the value sent to the num parameter.

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Now when I run this we can expect
the output to be five, let's double check.

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Awesome, just as I expected the output
here is 5 because when we called

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the add_two function we passed the integer
5 as an argument to the function.

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This value was received by our function
and stored in the variable num.

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Num, now referencing a value of five,

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can be used like any local
variable inside the function.

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I hope you're getting
the hang of arguments and

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parameters when you're ready,

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come join me in the next video to talk
about handling more than one parameter.

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Also don't forget that you're doing great
and you're learning things that are going

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to help you be more experienced and
capable programmer.

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If you're struggling, it's okay.

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Treehouse has tons of resources to help
you support you while you go through

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your coursework.

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The Treehouse community is an excellent
place to connect with other students and

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ask and answer questions.

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Watching videos a second time can
also help you absorb information.

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Sometimes you really need
to hear things two or

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three times before a concept
really starts to sink in.

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Think about a time when you've watched
a movie a second or third time.

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How much more did you pick up or notice,
learning programming is a lot like that.

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And finally don't hesitate to practice,
there is no wrong way to practice or

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learn and trying things out in
your terminal is a great way to

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understand what's happening in your code
without worrying about breaking anything.

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Taking advantage of Treehouse's practice
sessions is another way to gain

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a real advantage in
your skill development.

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Remember, just have fun and always keep
in mind that even professional and

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advanced programmers are always
learning and getting better too.