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For Loops
3:08For loops work their way over an iterable. Learn how to use them
The while loop is wonderful for
condition based looping.
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While this condition is true,
run this code.
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There's another type of looping
that I'd like to show off here.
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And it's for when you want to
iterate through a set of values.
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For instance,
think back to our banner example,
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that we used to talk about strings.
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And we can actually loop over
each letter in this banner.
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We can say for each letter in this banner,
run some code.
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Hey, let's do that in the shell here.
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I'll set up the banner object.
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Banner equals Happy birthday.
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So, the keyword is for and
we're gonna say letter in banner.
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Reads very nice, doesn't it?
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So for each letter in the banner,
I'm gonna press enter and
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you'll notice that there's three
dots now instead of the chevrons,
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instead of the three greater
than signs three dots.
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And that's because it's waiting for
us to finish this block of code.
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So I'm going to go one, two, three,
four and we'll print letter.upper.
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So what's happening, is each time through,
it's setting that letter variable.
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And now, I still have dots because
it's waiting for me to finish.
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So, here we go.
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Happy birthday.
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All capitals.
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What happens here, is that each time
through the loop, each one of these loops,
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this letter variable is set and you can
use it in the body of the function.
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The loop runs through each item on
this side of the in keyword and
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creates a new variable here
on the left side, that value.
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The right side of this in key
word has one requirement.
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It must be iterable.
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Now I find it helpful to break
that word iterable down to
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let's be able to be iterated.
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Cuz what we are doing here is looping
through or accessing each element.
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We're iterating through the values.
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Now strings have been
designed to be iterable.
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Each step through the loop provides
the next letter in the iteration.
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There are also many types in
Python that are iterable.
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And Python allows you to create your
own types that you can also iterate on.
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We'll get to more iterable
types here in future courses.
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Check the teacher's notes for more.
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Now, do you see the difference
between the while and for loops?
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For just runs from the start
to the finish of an iterable.
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It runs through each and
every value it's given from the iterable.
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With the addition of functions and
loops to your tool set,
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you are now ready to write some
pretty powerful applications.
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You might not believe me yet but
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the skills that you've picked up thus far,
input and output, conditional branching,
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math, exception handling, looping and
functions, are the foundations for
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almost all of the rest of the work
that you'll do in programming.
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There's always gonna be more to learn.
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But you're now armed with quite
an arsenal of solutions for
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just about any problem
that you might encounter.
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I get it though.
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It's hard to see how to combine all the
different skills that you just picked up.
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Let's do this.
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Let's wrap this course up with
a little simulation that will produce
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some working software that utilizes most
of your new found Python super powers.
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