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Iteration
4:35Let's iterate through each value in your list.
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One of the most common things
to do with lists is to loop or
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iterate through every item.
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Now, typically we iterate
through each value and
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then run some code against that item.
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Now, the most common way to do
this is with a for-in loop.
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We can use the for-in loop
because the list is iterable.
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That is, it's able to be iterated.
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Let's take a look at this
ability in the REPL.
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Okay, so let's take a look at this
meeting.py file in interactive mode.
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So we'll kick this off,
python -i meeting.py.
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And we have an attendees list.
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Remember?
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So we have our attendees here.
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And this is something we can iterate over.
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And the syntax is pretty clean.
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It's four and
in our case the thing is attendee.
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And this will be the variable that our
item is stored in for each iteration.
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And then the key word, in, and
then our list, which is again, attendees.
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And then we need to do
a colon to start the block.
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And then we can work with each one
of these items cuz they're already
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stored in the attendee variable.
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So, let's just print it out.
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So I'll say print(attendee).
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Awesome.
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So, I just want you to imagine that each
time through the loop that this variable,
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this attendee here is set
to the next item from here.
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So it just goes one through each right?
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So it goes, Ken, Alena,
Trevor, Ashley, James.
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And just sets that attendee
each time through the loop.
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Now, here's something that
you might not expect.
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The last value is actually
still available with that label
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even after the loop is done.
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So if I just type attendee here,
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you'll see that's set to
the last thing we looped through.
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So attendee is still set.
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I'm not sure you'll ever need that,
but you never know.
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One more think while we're here
in the REBEL, the end keyword.
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Just like how you can use it to see if
a string is inside another string, or
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we can also use it to see if one item
is in the list like for instance.
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I can see if actually
Ashley was in our list.
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I will just say hey,
is Ashley in attendees?
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True she is, awesome.
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So let's pop out of this and
let's switch over.
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To our wish list file.
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So I was thinking how about we make
this show every one of the items in our
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wish list.
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Let's just do the entire list.
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So, let's see, so we'll say,
let's make a little header here.
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So we'll do ("Books:"), and
we'll say for book, that's our thing,
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in books:, so that's gonna loop
through each one of this will be set.
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That'll be the book, that'll be the book,
that'll be that book, right?
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And so, I wanna make sure that
this is on 4, space is 4 here.
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Don't forget that.
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Here we go.
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For booking book,so now
we want to print them.
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And let's do a little bullet,
we will do a little asterisks there.
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You could use some Unicode
magic if you wanted to.
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So we'll look through each one of these
and then print out the books, cool.
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Let's go ahead,
let's save that and then run it.
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So python -i wishlist.py.
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Awesome, beautiful,
you know what while I'm here
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id like to add another type
of product to my wish list.
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So my other addiction is video games I've
added my wish list from a couple days ago
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to the teachers note so
lets just copy and paste that.
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Paste that up here.
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So there we go video games.
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Breath of a Wild,
wish I was playing right now.
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And things don't stay
on this list very long.
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Confession I've already
bought all these video games.
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I'm a little bit obsessed.
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They're all so good.
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Anyways, let's just
display my outdated list.
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So I think I'd like to do the same thing,
I'd like to add a title and
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then do a layout, I suppose I could
just copy and paste the code, but
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my don't repeat yourself my
dry spidey sense is going off.
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I don't wanna duplicate that code,
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now what if I want to change
the way it's displayed,
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I have to do that in two places so here
let's solve that problem with a function.
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So how about I make a function that
expects parameters of the display name?
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You know, like, is it a book or
a video game, and also the list.
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Let's do that.
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But first, let's take a quick break,
because I want to show you the gotchas
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surround the passing a mutable object,
like a list around.
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Take a quick break, and
come back refreshed and
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we'll tackle this
mutability issue head on.
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