WEBVTT

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So, in the previous two videos
we've talked about lists and

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figured out how they work in Python.

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So, what I'm gonna do now is just
run you through another example

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of a more complicated version and
then move onto a challenge.

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Now, what we're gonna do is we're gonna
use a concept we've used earlier,

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which is a meal in a cafe.

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So, what I'm going to do
is type in some code.

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I'm going to actually delete what

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we've got on the screen here
because we don't need it anymore.

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And I'm going to start typing menu
equals two empty square brackets,

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which is an empty list.

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Then we do menu.append.

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Notice the square brackets.

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Egg, spam, bacon.

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Bacon like so.

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So that's our first entry and I'm just
gonna copy the first part of this so

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I can copy it and
paste it rather than type it each time.

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The next menu option is going to be egg,
sausage, bacon.

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Next one is going to be egg, and spam.

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Next one, egg, bacon, spam.

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Next one, egg, bacon,

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sausage, spam.

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Next one is going to be spam,
bacon, sausage, and more spam.

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Oops.

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Then we're going to have two more here.

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Spam, egg, spam.

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Spam, bacon, spam.

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And the last one we're gonna have is spam,

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egg, sausage, spam.

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So first things first,
you might be wondering why is there so

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much spam in these meals?

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Well, the menu's actually taken
from a Monty Python sketch.

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And if you want to search the Internet for
Monty Python spam sketch,

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then you can find out more about that.

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You actually watch it on YouTube as well
when you feel you need to take a break.

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So incidentally that sketch is the reason
we now refer to junk email as a spam.

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But anyway so what we've done here is
we've actually created the empty list

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as you saw on line one.

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And we then went through and
appended each of the meals to it.

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And of course each of the meals as you'll
now see in square brackets is actually

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listed its own right containing
the details of that meal.

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So we can actually print something out.

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We can type print Menu.

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Actually run that.

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We can actually see the entries.

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So it's a little bit hard to see because
it's actually menus within menus,

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but you can sort of see that there's
the first on there on the screen,

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separated by a comma, and they've
each got their own square brackets to

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indicate they're actually each
a list in their own right.

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Now that we've actually got a list and
we've got a lot of entries.

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We can actually start writing a for
loop and

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actually testing to see
how the in operator works.

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So we could do something like for
meal in menu.

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Then we could put if not spam

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in meal, print meal.

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So if we actually run this and

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I'll just comment out this first line
here, just to remove the confusion.

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And what that should do, and what that
actually does is only shows the entry

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which is on line three
that doesn't contain spam.

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And again each of the items on
the menu are themselves lists.

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So the for loop here initially, for
meal in menu, is going through and

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grabbing a list with each iteration.

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So the first time it goes through the for

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loop, the meal variable is set to the
list, which is the first list in the list.

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So to speak.

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And from there we can put
if not spam in meal, and

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that's actually searching through that
individual list, the list that of

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course is sort of a sub-list of
a major list, if that makes sense.

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Then we're actually determining that that
wasn't in there, and we're only printing

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out the contents if the word spam wasn't
found as one of the list entries.

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So again, you can see that
Python is extremely powerful,

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the way it's been designed and how it
actually handles this, is like this.

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Okay, so it's time for a challenge.

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What I am going to do is go to the first
line and paste in the challenge.

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And that should be without spam.

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So let's actually talk now about what
the challenge is actually about.

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So what you need to do is
add to the program below.

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So that if it finds a meal
without spam in it,

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that it then prints out each of
the ingredients of the meal.

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At this stage you can see that we printed
out everything, but you need to actually

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go through each individual item,
rather than just printing the entire list.

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So you'll need to set up the menu as
we did in lines five to 13 there.

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So type that in to start with, and
then you'll need to modify the for

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loop in some way.

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This code down here.

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So then, basically prints out
each ingredient separately,

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rather than just printing out just
the list as it's currently doing.

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Okay?
So, pause the video.

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Go away and actually see if you can
come up with a solution to that.

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When you're finished,
come back and check my solution.

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Okay so how did you get under?

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Did you figure it out?

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So we're actually on the right track here.

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We've actually got a lot of
the code in build already.

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So we've got the first loop the outside
loop with is going through each meal

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that's in the menu list
then grabbing that meal.

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So that needs to stay there.

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We also need to put the if not in there,
so

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that we only get the meals
that haven't got spam in them.

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And we can print out this initial list.

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We can leave that in there like
we're seeing on the screen.

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But what we then need to do is
iterate through the list of

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entries in this particular meal and
print those out.

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So to do that, we stay at this indentation
level cuz we're only processing a meal

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if it doesn't contain spam.

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And we type in for ingredient in meal,

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colon print ingredient,
so that is literally it.

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So we are taking it to the next level
we're actually now going through the list

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from the meal.

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So first, the outer entry, the initial for
loop, that was the master list,

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the list of all the menus, whereas the
inner list for ingredient in meals is just

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as you can see it's actually
the ingredients within a specific list.

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So, if we actually run that now.

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We finally get the output egg,
sausage, bacon, and

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we're getting that because there's only
one entry in here that hasn't got spam..

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And then also, we're then cycling
through that list that we retrieved, and

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actually printing out
the individual items.

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So, that's it.

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That's the challenge,
I hope you did well with that.

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And, I hope you've got
a lot out of this section.

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And, I'll see you in the next video.