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Iteration

4:35 with Craig Dennis

Let's iterate through each value in your list.

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video_games = [
    "The Legend of Zelda: Breath of the Wild",
    "Splatoon 2",
    "Super Mario Odyssey",
]

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[MUSIC] 0:00

One of the most common things to do with lists is to loop or 0:04

iterate through every item. 0:07

Now, typically we iterate through each value and 0:09

then run some code against that item. 0:12

Now, the most common way to do this is with a for-in loop. 0:14

We can use the for-in loop because the list is iterable. 0:18

That is, it's able to be iterated. 0:22

Let's take a look at this ability in the REPL. 0:24

Okay, so let's take a look at this meeting.py file in interactive mode. 0:28

So we'll kick this off, python -i meeting.py. 0:33

And we have an attendees list. 0:39

Remember? 0:41

So we have our attendees here. 0:43

And this is something we can iterate over. 0:44

And the syntax is pretty clean. 0:46

It's four and in our case the thing is attendee. 0:49

And this will be the variable that our item is stored in for each iteration. 0:53

And then the key word, in, and then our list, which is again, attendees. 0:58

And then we need to do a colon to start the block. 1:04

And then we can work with each one of these items cuz they're already 1:07

stored in the attendee variable. 1:10

So, let's just print it out. 1:12

So I'll say print(attendee). 1:13

Awesome. 1:18

So, I just want you to imagine that each time through the loop that this variable, 1:20

this attendee here is set to the next item from here. 1:24

So it just goes one through each right? 1:27

So it goes, Ken, Alena, Trevor, Ashley, James. 1:29

And just sets that attendee each time through the loop. 1:31

Now, here's something that you might not expect. 1:34

The last value is actually still available with that label 1:37

even after the loop is done. 1:40

So if I just type attendee here, 1:42

you'll see that's set to the last thing we looped through. 1:43

So attendee is still set. 1:47

I'm not sure you'll ever need that, but you never know. 1:48

One more think while we're here in the REBEL, the end keyword. 1:51

Just like how you can use it to see if a string is inside another string, or 1:55

we can also use it to see if one item is in the list like for instance. 1:59

I can see if actually Ashley was in our list. 2:03

I will just say hey, is Ashley in attendees? 2:04

True she is, awesome. 2:10

So let's pop out of this and let's switch over. 2:12

To our wish list file. 2:15

So I was thinking how about we make this show every one of the items in our 2:20

wish list. 2:24

Let's just do the entire list. 2:26

So, let's see, so we'll say, let's make a little header here. 2:27

So we'll do ("Books:"), and we'll say for book, that's our thing, 2:30

in books:, so that's gonna loop through each one of this will be set. 2:36

That'll be the book, that'll be the book, that'll be that book, right? 2:41

And so, I wanna make sure that this is on 4, space is 4 here. 2:46

Don't forget that. 2:51

Here we go. 2:53

For booking book,so now we want to print them. 2:54

And let's do a little bullet, we will do a little asterisks there. 2:57

You could use some Unicode magic if you wanted to. 3:01

So we'll look through each one of these and then print out the books, cool. 3:05

Let's go ahead, let's save that and then run it. 3:09

So python -i wishlist.py. 3:12

Awesome, beautiful, you know what while I'm here 3:18

id like to add another type of product to my wish list. 3:22

So my other addiction is video games I've added my wish list from a couple days ago 3:25

to the teachers note so lets just copy and paste that. 3:30

Paste that up here. 3:35

So there we go video games. 3:38

Breath of a Wild, wish I was playing right now. 3:41

And things don't stay on this list very long. 3:43

Confession I've already bought all these video games. 3:46

I'm a little bit obsessed. 3:48

They're all so good. 3:49

Anyways, let's just display my outdated list. 3:50

So I think I'd like to do the same thing, I'd like to add a title and 3:52

then do a layout, I suppose I could just copy and paste the code, but 3:57

mine don't repeat yourself my dry spidey sense is going off. 4:02

I don't wanna duplicate that code, 4:06

now what if I want to change the way it's displayed, 4:08

I have to do that in two places so here let's solve that problem with a function. 4:11

So how about I make a function that expects parameters of the display name? 4:16

You know, like, is it a book or a video game, and also the list. 4:20

Let's do that. 4:23

But first, let's take a quick break, because I want to show you the gotchas 4:24

surround the passing a mutable object, like a list around. 4:27

Take a quick break, and come back refreshed and 4:31

we'll tackle this mutability issue head on. 4:33

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