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All About Returns
5:03How to get data out of functions using returns.
All right.
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Now that we've recapped what we know about
functions, let's get to the next concept,
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getting data out of functions.
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Since the code in a global context
can't access what's in a local context,
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functions might seem pretty limiting.
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What's the point if what happens
inside them stays inside them?
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Well, programmers have a solution for
this, it's called returning.
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Returning a value from a function
is extremely common, and
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it's a tool you'll use all the time, and
you only need to know one word, return.
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Let's look at an example, feel free to
just watch and follow along with my
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workspace, you'll have an opportunity
to try on your own shortly.
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So here we have a function
called two_plus_two.
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Like the name suggests,
this function adds 2 + 2,
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and assigns the value to
a variable called val.
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Let's call the function and
run the program.
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Well, that's weird.
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It doesn't look like much
if anything has happened.
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The variable val was created and
assigned a value in the background, but
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we didn't do anything with it, so
we can't see or use that value.
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And none of this was
really very helpful to us.
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Okay, so let's try returning
the variable from the function so
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we can access it outside
the function in our global context.
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To do that, I'll go back to our function.
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Create a new line, and
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I'll use the keyword return followed
by the value I'm returning.
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Now, you can return a specific value
like a string or an integer, or
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you can return a variable.
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When you return a variable,
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the value assigned to the variable
is what gets returned.
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So in this case, our function will
be returning the integer 4, but
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we’re going to write return val.
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Now, I’m going to save this and
try to run it again.
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Wow, that’s kind of weird, it still
doesn't look like anything happened.
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But actually that makes sense because the
value was returned from the function, but
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we still didn't do anything with it.
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So let's break this down.
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When you call a function
that returns the value,
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the return value is sent
back to the function call.
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The function call now behaves in
the same way a variable might.
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It's holding a value that can be printed,
assigned to another variable, or
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used in an expression.
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So we're going to try all of these.
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First, I'll print it.
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Now I'll save and run again.
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Cool, it prints out 4, which is
the value returned from the function.
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But a more common way to handle function
returns is to assign them to a variable,
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that looks like this.
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So, in this example, I've created
a variable called sum, and the value
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that we're assigning to sum is the return
value from the call to two_plus_two.
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To break that down further,
when the Python interpreter processes
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the right-hand side of the statement,
it calls the two_plus_two function,
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which then calculates the value
of 2 + 2 and returns it back.
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The interpreter then takes
that returned value and
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assigns it to the new variable, sum.
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Let's print out the value
of sum to demonstrate this.
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Now save and run.
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This also prints out 4.
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And as you can see,
printing the function call is equivalent
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to assigning the function call to
a variable and printing that variable.
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Now finally, we can use
the function call in an expression.
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Our function is returning an integer.
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So let's try to take that value and
multiply it by two.
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How about you give this a try on your own?
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Pause the video here and
open up the attached workspace.
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Add a return statement inside
the two_plus_two function
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that returns the val variable.
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After the function, print out the product
of the return value and the number 2.
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When you're done,
un-pause the video to see the solution.
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Okay, how did it go?
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To use the function call in an expression,
pretend it's a regular integer or
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variable.
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So, in the following example expression,
4 * 2,
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we can replace the 4
with the function call.
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Then we can print it out.
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So we'll save and run.
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Awesome, this prints out 8,
just as expected.
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That's because the return value
from the function is 4 and
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we multiply that by 2
in our print statement.
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Great work.
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In the next video, we'll expand on our
function discussion to show more about how
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useful they can be and
why we'd want to use them.
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See you soon and keep on coding.
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