3.txt

00:00 Lists are actually pretty simple.
00:02 They're probably one of the things you're
00:03 going to deal with the most in your Python journey
00:06 and the easiest way to demonstrate it is
00:09 to just create one right here of numbers.
00:13 So let's create a stereotypical list, all right.
00:17 We do that by using the square brackets
00:20 and we're going to create five entries in that list.
00:26 So this list contains five items.
00:29 Okay. Now, because we're dealing with numbers specifically,
00:32 we don't have to put the quotes around it, okay.
00:38 If we were dealing with strings that's what we do,
00:41 but we're dealing with just numbers
00:43 so let's just leave it plain like that.
00:46 So that's our numlist.
00:48 We'll just call it back so you can see what it looks like.
00:51 There you go.
00:53 So it's now a list of five numbers, okay.
00:55 1, 2, 3, 4, 5.
00:57 One of the cool things you can do
00:58 with a list is you can actually reverse it.
01:01 Okay.
01:02 So, now need to write some nifty code
01:04 that will go through, parse it,
01:06 and put all the values in back to front.
01:10 We can just do numlist.reverse()
01:13 Call numlist back and there you go,
01:16 5, 4, 3, 2, 1.
01:19 Now we can do that again.
01:25 Okay, and we're back to one, two, three, four, five.
01:29 Now, if we actually go back,
01:34 one thing we can do, is we can actually sort the list.
01:40 So numlist.sort(), okay.
01:45 And there you go 1, 2, 3, 4, 5 again.
01:47 And this is very handy because you can actually sort
01:49 with letters as well.
01:52 Now let's say we want to actually print out all
01:54 of the values inside num list.
01:57 How do we do that?
01:58 We can use a four loop, okay?
01:59 So we can go four num in numlist, print(str(num)).
02:08 So we hit enter and there are our five numbers,
02:12 1, 2, 3, 4, 5
02:14 So it's pretty powerful.
02:15 There's with just this basic ideology you can get a lot
02:18 of stuff done in Python code.
02:22 Now one of the other ways you can actually create a list is
02:25 to call the list function against a certain string.
02:31 Let's say we have a string called -
02:33 we have a variable called mystring.
02:36 And we assign it to string Julian.
02:41 Okay, so mystring is Julian.
02:44 Well how do we convert that into a list?
02:46 We simply call list against it.
02:49 So list(mystring) is Julian.
02:53 And there you go, you see my name has just been chopped up
02:57 so that each letter, or each character I should say,
03:01 is now a string value inside this list.
03:06 Right. So, what can we do?
03:08 We can assign that so l = list(mystring).
03:16 So we're assigning this here to the variable l, alright.
03:23 And we'll just call that back.
03:25 And it's Julian.
03:26 Now what are some interesting things we can do with this?
03:28 Well, there's actually quite a lot.
03:30 We can actually reference the values
03:32 by their position, by their index, inside that list.
03:37 So we can go l[0] is J.
03:42 We can go l[4] is A.
03:47 You can see we got J there, we got A there.
03:51 Very handy.
03:52 What else can we do?
03:53 Well there are a few other functions we can call here.
03:55 We can go pop, and what pop will do it's actually going
04:00 to return the last letter from this list.
04:08 So, the letter N is going to be returned.
04:11 But at the same time,
04:13 it's going to be removed from the list.
04:16 So my name is now Julia.
04:18 Right.
04:21 We can then insert it back in.
04:23 And we use insert for that.
04:28 Now when we insert, we actually,
04:30 if you look at this tool tip here that's cheating,
04:33 you can see we have to specify an index and then the object.
04:37 So what position are we inserting the letter N
04:42 into this list?
04:43 Well, we're going to insert it into position 0,
04:47 1, 2, 3, 4, and 5
04:51 5 is going to be on the end, so position five.
04:54 And what are we inserting?
04:55 We're inserting the letter N.
04:57 All right, it's an actual string.
05:02 Now when we call the list, there we go,
05:05 it's rebuilt with the letter N.
05:07 Another interesting this we can do is
05:09 we can actually replace any of these with any other letter.
05:15 So we can go l[0], which we know will actually return J,
05:20 but we can replace J.
05:22 So L[0] is going to be B.
05:30 So, l is now Bulian.
05:35 Okay?
05:36 Ya, a little play on words.
05:37 Let's go with that.
05:39 Now if we wanted to get rid of the B,
05:42 we could actually delete it or we could pop it.
05:45 The difference is, as I've said before,
05:47 pop will return the letter in that position,
05:53 where as now with the delete option
05:56 it will actually delete it.
05:58 You won't even know what you're deleting.
06:00 It doesn't return anything, it just deletes.
06:03 So if we want to delete that zero we just have
06:05 to type del(l[0]
06:13 and there's the B gone.
06:15 All right?
06:16 Next we can do l.insert().
06:21 We'll choose index position zero.
06:24 And this time we'll put an M in.
06:28 l is now Mulian, okay.
06:31 And now, even better, with pop,
06:34 let's say we do want to return something, we can go l.pop(),
06:39 but now we can actually specify a position, an index.
06:43 So we can go l.pop(0), we get the M returned,
06:49 and the M has also been removed
06:51 from position 0 in the list.
06:54 So those are some cool little nifty tricks
06:57 you can keep up your sleeve, add them to your book,
07:00 because when it comes to lists, you'll end up dealing
07:02 with them quite a lot.
07:03 So knowing how to pop and how to delete and insert
07:07 and append, which is another one I'll show you quickly.
07:11 l.append(), let's add S.
07:21 We can append, append will always add right at the end
07:26 into the last position.
07:29 So definitely keep all of these handy.
07:31 You'll be using them quite a lot.