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[MUSIC]

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Hi again, welcome to the final stage
of functions, packing and unpacking.

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We've talked a lot about the functions
part of this course so far,

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how are you feeling?

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Do you feel confident in writing basic
functions, passing arguments and

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receiving returns?

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If so, then keep moving forward to
learn about packing and unpacking.

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If not, then before moving on, try to
review the content in the course so far,

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check out the Treehouse community, and
practice by writing your own functions and

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calling them to see how things work.

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So what's packing?

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Well, in the last section, we talked about
passing multiple arguments to a function,

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and how we receive each of those arguments
into its own parameter, or variable.

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Packing expands on this concept and let's
us do something potentially more useful,

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and certainly more cool, let's dive in.

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The basic concept of packing is
compressing multiple values into

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one tuple.

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You can do this anywhere
in your Python code,

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but it's very commonly used when passing
multiple arguments to a function.

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Your function receives
the multiple arguments and

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packs them up into a single parameter.

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This parameter now references a tuple
where the elements of the tuple

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are the many arguments passed to
the function, kind of random right?

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Well not so much, there are definitely
going to be times in your python career

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when you want to write a function
that receives data, but

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you're not sure what that data
will look like ahead of time.

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There's also going to be times
when receiving all of your

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arguments into one tuple, cuts down on
the amount of code you need to write, or

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drastically simplifies future steps.

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Let's take a look, for
now just follow along with what I'm doing,

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don't worry about trying
to code along with me.

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So here we have a function called packer
that receives multiple arguments.

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packer prints each argument
onto its own line.

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This is a pretty basic and
pointless function but humor me,

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we're just using it for
demonstration purposes.

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So I'm gonna write a call to this packer
function where each argument is a string.

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Now I'm gonna run this, just so

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you can get a picture of what
it looks like without packing.

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Each argument has been received
into its own parameter and

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then it's printed out on its own line.

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Now, if we wanted to take
advantage of packing in Python and

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pass these four arguments into one tuple,

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we'd change our function
definition to look more like this.

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We'll get rid of each of these arguments,

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and only use one, and
then we can print args on its own.

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Our function call is gonna
remain exactly the same.

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Now, when we run this, we'll see that each
of our four individual arguments have been

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converted to a tuple and
are printed as such, let's take a look.

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So what did we do here?

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The secret is in the asterisk,

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the little star at the beginning
of the parameter name.

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This star tells Python that we intend to
pack all the arguments sent the function

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into whatever parameter
immediately follows the star.

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This means when packer is called,
and those four arguments are passed,

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the function will receive them all into
one tuple stored in parameter args.

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args can then be used in the body of the
function, just like any other parameter.

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And because tuples are iterable, if we
still wanted each argument print on its

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own line, we can still do that,
but we'll use a loop instead.

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Now I'll save,
I'll come back down to my terminal.

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I'll clear this out to leave
a little more room, okay, so

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when I run the file again, Cool.

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As we iterate over args each element in
the tuple is printed to its own line.

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The parameter args with the asterisk
before it is a very common pattern in

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Python, you'll see it a lot.

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Let's dive into args a little more in the
next video with a more practical example.