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How to get data out of functions using returns.
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All right.
0:00
Now that we've recapped what we know about
functions, let's get to the next concept,
0:01
getting data out of functions.
0:05
Since the code in a global context
can't access what's in a local context,
0:07
functions might seem pretty limiting.
0:11
What's the point if what happens
inside them stays inside them?
0:14
Well, programmers have a solution for
this, it's called returning.
0:18
Returning a value from a function
is extremely common, and
0:22
it's a tool you'll use all the time, and
you only need to know one word, return.
0:26
Let's look at an example, feel free to
just watch and follow along with my
0:31
workspace, you'll have an opportunity
to try on your own shortly.
0:34
So here we have a function
called two_plus_two.
0:38
Like the name suggests,
this function adds 2 + 2,
0:41
and assigns the value to
a variable called val.
0:45
Let's call the function and
run the program.
0:49
Well, that's weird.
1:02
It doesn't look like much
if anything has happened.
1:04
The variable val was created and
assigned a value in the background, but
1:07
we didn't do anything with it, so
we can't see or use that value.
1:11
And none of this was
really very helpful to us.
1:14
Okay, so let's try returning
the variable from the function so
1:18
we can access it outside
the function in our global context.
1:21
To do that, I'll go back to our function.
1:25
Create a new line, and
1:28
I'll use the keyword return followed
by the value I'm returning.
1:29
Now, you can return a specific value
like a string or an integer, or
1:34
you can return a variable.
1:38
When you return a variable,
1:39
the value assigned to the variable
is what gets returned.
1:41
So in this case, our function will
be returning the integer 4, but
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we’re going to write return val.
1:47
Now, I’m going to save this and
try to run it again.
1:50
Wow, that’s kind of weird, it still
doesn't look like anything happened.
1:57
But actually that makes sense because the
value was returned from the function, but
2:01
we still didn't do anything with it.
2:05
So let's break this down.
2:07
When you call a function
that returns the value,
2:09
the return value is sent
back to the function call.
2:12
The function call now behaves in
the same way a variable might.
2:15
It's holding a value that can be printed,
assigned to another variable, or
2:19
used in an expression.
2:23
So we're going to try all of these.
2:24
First, I'll print it.
2:26
Now I'll save and run again.
2:32
Cool, it prints out 4, which is
the value returned from the function.
2:35
But a more common way to handle function
returns is to assign them to a variable,
2:39
that looks like this.
2:44
So, in this example, I've created
a variable called sum, and the value
2:53
that we're assigning to sum is the return
value from the call to two_plus_two.
2:58
To break that down further,
when the Python interpreter processes
3:04
the right-hand side of the statement,
it calls the two_plus_two function,
3:07
which then calculates the value
of 2 + 2 and returns it back.
3:11
The interpreter then takes
that returned value and
3:16
assigns it to the new variable, sum.
3:18
Let's print out the value
of sum to demonstrate this.
3:21
Now save and run.
3:29
This also prints out 4.
3:34
And as you can see,
printing the function call is equivalent
3:36
to assigning the function call to
a variable and printing that variable.
3:39
Now finally, we can use
the function call in an expression.
3:44
Our function is returning an integer.
3:48
So let's try to take that value and
multiply it by two.
3:50
How about you give this a try on your own?
3:53
Pause the video here and
open up the attached workspace.
3:55
Add a return statement inside
the two_plus_two function
3:59
that returns the val variable.
4:02
After the function, print out the product
of the return value and the number 2.
4:05
When you're done,
un-pause the video to see the solution.
4:10
Okay, how did it go?
4:14
To use the function call in an expression,
pretend it's a regular integer or
4:16
variable.
4:19
So, in the following example expression,
4 * 2,
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we can replace the 4
with the function call.
4:25
Then we can print it out.
4:33
So we'll save and run.
4:40
Awesome, this prints out 8,
just as expected.
4:45
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.
4:51
Great work.
4:54
In the next video, we'll expand on our
function discussion to show more about how
4:55
useful they can be and
why we'd want to use them.
4:58
See you soon and keep on coding.
5:01
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