Lecture 2.3 - Function Arguments

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From the course by University of California, Irvine

The Raspberry Pi Platform and Python Programming for the Raspberry Pi

1273 ratings

University of California, Irvine

The Raspberry Pi Platform and Python Programming for the Raspberry Pi

1273 ratings

Course 4 of 6 in the Specialization An Introduction to Programming the Internet of Things (IOT)

The Raspberry Pi is a small, affordable single-board computer that you will use to design and develop fun and practical IoT devices while learning programming and computer hardware. In addition, you will learn how to set up up the Raspberry Pi environment, get a Linux operating system running, and write and execute some basic Python code on the Raspberry Pi. You will also learn how to use Python-based IDE (integrated development environments) for the Raspberry Pi and how to trace and debug Python code on the device. Please note that this course does not include discussion forums.

From the lesson

Module 3

We present the basics of the Python programming language to prepare you for programming on the Raspberry Pi. Many languages can be used but Python is the most convenient for the Raspberry Pi because convenient APIs are provided for basic operations such as controlling the pins. Python is a powerful language with useful features that we will present so that you can use these features to control the Raspberry Pi.

Lecture 2.1 - Strings6:04

Lecture 2.2 - Functions4:01

Lecture 2.3 - Function Arguments3:33

Meet the Instructors

Ian Harris
Professor
Department of Computer Science

[MUSIC]

Functions can be called with arguments or parameters.

Arguments are basically input data to the function.

So in my test function that I did in the last set of slides,

it didn't have any arguments.

It just printed something, it didn't need any input data.

But often, functions require input data to process on.

So those input datas, you call those arguments.

A function can take arguments, which are values that are bound to variables inside

the program at execution time.

So any arguments that you want to pass as information to the function,

you list them inside the parenthesis when you make the function call.

And also inside parentheses when you're doing definition of the function, so

we'll see that here.

So say, I wanna define something that computes the area of a circle.

So I say, def circle_area.

Now if you wanna compute the area of a circle that's pi r squared,

where r is radius.

So I have to take an argument,

you can't figure out the area of a circle without knowing the radius.

So I'm gonna make radius an argument, I call it rad here.

So I put rad in parentheses to say,

look this function has to take one argument, which I will call rad.

Then inside it, I just say print 3.14,

which is approximately pi times rad times rad.

My simple version, that's pi rad squared r squared.

And so when I run that, when I want to execute that.

I call the function circle_area, I pass it 2 as an argument.

That's the radius I want.

I put 2 inside the parenthesis and then it computes it and prints out the results.

So that's how you pass arguments to functions.

So you have to define it in the definition, you name the argument.

And then at run time that two, when you call circle area capacity two,

that two will be bound to rad.

That variable red and so two will be rad.

So it will print out 3.14 times 2 times 2,

it will substitute the 2 in for the rad.

Now functions in addition to taking input values,

they can also return output values.

Those are called return values.

So function can return values if you use a return instruction at the end of

the function.

And notice on my last program, I didn't use return I said, print,

which just prints it to the screen.

That's different than returning a value.

Returning a value, when you return a value,

the whole function call is substituted for whatever the return value is inside

whatever expression you use the function call.

So if you use the function call inside a bigger expression.

So if I say, x plus 5 plus circle_area and I call it with a 2,

then it'll compute with the circle areas with a two.

If I return that, it'll substitute that in.

So, it'll do 5 plus whatever the return value is.

So, I'll give you an example.

So I got my circle_area, I define it.

And this time, I say, return.

Return 3.14 * rad * rad.

Now I say circle_area (2).

If I just call circle_area (2), it returns 12.56.

But if I say, a 3 plus circle_area (2), it return 15.56,

because it just takes a whatever circle_area (2) returns and

it substitute the grade in there into a bigger expression.

3 plus circle_area (2).

So 3 plus 12.56 and the return is 15.56.

So that's a return value and that's useful a lot of times.

Thank you.

[MUSIC]

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