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How about sending data to a function?
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Welcome back.
0:00
Now that we've discussed
returning values from functions,
0:01
we're going to build on this by learning
how to send values to functions.
0:03
We've been using some pretty
simple examples so far.
0:07
Our function that adds two plus two
together wasn't very interesting,
0:09
even after we returned a value from it.
0:13
You might be thinking I still don't
get why functions are so useful.
0:15
Well, let's expand on this.
0:19
Our 2 plus 2 function
would be a lot more useful
0:21
if we could use it to add the number 2 to
any integer and we can totally do that.
0:24
Just like functions can send values
back via a return, functions can receive
0:29
values too and they can see, access and
use those values inside the function.
0:34
This is all done by what’s called
passing an argument to a function.
0:39
There are two parts to this.
0:43
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.
0:48
Have you ever wondered about those
pesky parenthesis we have to
0:53
add when defining or calling the function?
0:55
Those parens are where the sending and
receiving of values takes place.
0:58
Let's revisit our two plus two function.
1:02
Okay, first, I'm gonna change its name.
1:05
Instead of 2 + 2, I'll call it add_two.
1:07
This new name makes more sense because
we're gonna modify this function so
1:13
it now adds 2 to whatever
integer it receives.
1:17
Now inside the parens,
I'm gonna create a variable.
1:20
I'm gonna call it num.
1:23
Right now num has no value, it won't be
assigned a value until the function is
1:25
called and a value is passed but
we'll get to that in just one moment.
1:29
Now that we've created
a variable inside the parens,
1:33
this special kind of variable is
known as a parameter by the way.
1:36
We can use it inside of our function
just like any other local variable.
1:39
That means we can change the body
of our function like this.
1:43
What we've done here is rewrite our
function so that it can receive a value,
1:50
which is stored in the parameter
variable called num.
1:53
And then we can use that
value inside the function.
1:57
So how do we send that
value to our function?
2:00
Well, this happens when we call it.
2:03
First we'll write a regular function
call to the add_two function.
2:04
To send a value,
we add it inside the parens.
2:12
This value is called an argument.
2:15
An argument can be any Python data type or
expression that evaluates to a value.
2:17
This means you can pass in an integer,
a string, a function call, and
2:22
even other Python data types that
you haven't learned about quite yet.
2:26
In our case,
we're just gonna be passing an integer.
2:29
Let's pass the number 5.
2:32
Now, like we learned
earlier in this course,
2:35
not much will be visible to us
if we run our program right now.
2:37
To add some clarity to what's going on
behind the scenes, I'll add a print
2:40
statement inside our function that prints
out the value sent to the num parameter.
2:44
Now when I run this we can expect
the output to be five, let's double check.
2:53
Awesome, just as I expected the output
here is 5 because when we called
3:05
the add_two function we passed the integer
5 as an argument to the function.
3:09
This value was received by our function
and stored in the variable num.
3:15
Num, now referencing a value of five,
3:18
can be used like any local
variable inside the function.
3:21
I hope you're getting
the hang of arguments and
3:25
parameters when you're ready,
3:27
come join me in the next video to talk
about handling more than one parameter.
3:29
Also don't forget that you're doing great
and you're learning things that are going
3:32
to help you be more experienced and
capable programmer.
3:35
If you're struggling, it's okay.
3:39
Treehouse has tons of resources to help
you support you while you go through
3:41
your coursework.
3:44
The Treehouse community is an excellent
place to connect with other students and
3:45
ask and answer questions.
3:48
Watching videos a second time can
also help you absorb information.
3:50
Sometimes you really need
to hear things two or
3:54
three times before a concept
really starts to sink in.
3:56
Think about a time when you've watched
a movie a second or third time.
3:59
How much more did you pick up or notice?
Learning programming is a lot like that.
4:02
And finally don't hesitate to practice,
there is no wrong way to practice or
4:06
learn and trying things out in
your terminal is a great way to
4:10
understand what's happening in your code
without worrying about breaking anything.
4:13
Taking advantage of Treehouse's practice
sessions is another way to gain
4:18
a real advantage in
your skill development.
4:21
Remember, just have fun and always keep
in mind that even professional and
4:24
advanced programmers are always
learning and getting better too.
4:28
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