- Growing up, my siblings and I loved to go to the carwash.
And depending on how much money
my parents were willing to pay,
we could have a different experience each time.
For $6, we would get the most basic wash,
white foam, one rinse and a drip dry.
But if they were willing to spend $12,
then we could get tricolor foam, two rinses
Just like the carwash, in programming,
we often want to provide different outputs to our users
based on some input.
Functions allow us to do this,
in fact, let's go over to VS Code
to see a function that simulates our carwash experience.
We're here in 05_03_begin.
We have this function defined on line number one, wash_car,
and then we have our open and close parentheses
Inside, we have our carwash steps.
First, we have the steps for the Platinum car wash
on lines two through four.
Then, down on lines six through eight,
we have the steps for the Basic car wash.
Let's go ahead and call this function using its name.
We'll do that down here on line number 10.
Wash_car and then a set of open and close parentheses.
and go down to Run Python File in Terminal.
And you probably guessed it,
when the amount paid is $12
and the Basic steps only if the amount paid is $6?
How do you think we can do that?
I hope the first thing that came to your mind
is an if statement.
Let's pretend we have the amount paid
stored in a variable named amount_paid,
So let's close this down
and then, we'll come back inside of our function
and we'll start right on line number two,
we'll add our if statement.
So, if the amount paid
is equal to 12, this is for the Platinum wash,
Remember, we have to indent the statements,
that all three of these print statements belong to this if.
Next, we'll come down to line number seven
and we'll create another if statement,
this time it's for the Basic car wash,
if the amount_paid
is equal to six, then we're going to do the steps
in the Basic car wash.
Once again, make sure you indent the statements
that you want to include inside your if.
So now, let's save it and run our file again.
And look, we get an error, Python is letting us know
so we need to do something to bring this variable
inside of our functions world.
In order to do that, let's close down this window
and we're going to come up to where we've defined our function,
inside of our open and close parentheses,
then we're going to include amount_paid,
this is how we let our function know
Let's save our code now.
In programming, this variable
has a special name, a parameter.
to change their behavior based on some input.
Let's go ahead and run our code again.
But look, we get an error,
but what does that mean?
What is a positional argument?
Well, similar to how we have parameters as the name
for the variables we use in our function definition,
we have arguments as the name we use
for the values that we give to our functions.
And we give our functions arguments
by placing a value between the open and close parentheses
in the function call.
Let's do that now.
We're going to close down this pane
and then here, on line number 12,
where we call our function, let's give it the number six
in between the open and close parentheses,
this is going to serve as our argument.
After we save our file and run it, let's notice the output.
And indeed, we get all the steps for the Basic car wash.
On your own, provide 12 as the argument to the function
and enjoy the Platinum wash experience.
One thing to note is that sometimes parameters and arguments
are used interchangeably, you'll have to rely
on the context to figure out the meaning,
but don't despair, the key thing to know
is that functions have the ability to change their behavior
based on their parameters and arguments.