Python Lists

Quick reference

• 00:04 Okay, in this video, I want to talk about Python Lists.
• 00:07 And Lists are a very important data structure in Python.
• 00:10 And they are just what they sound like, they're lists.
• 00:13 They are a way to keep track of different items.
• 00:16 So to create a list in Python, it's actually really easy.
• 00:19 Just like a variable, we name it.
• 00:21 So let's call this names and right now, this looks just like a variable.
• 00:26 And in fact it sort of is a variable.
• 00:27 It's just going to hold a list, a list of items.
• 00:31 So to create a list, we use these square brackets and now inside of these brackets,
• 00:35 we can have as many items as we want.
• 00:38 We just separate them all with commas.
• 00:40 So we're going to create a list of names here and let's create some.
• 00:43 So let's go John, let's go Tina, and let's go Bob.
• 00:50 And you'll notice I'm using double quotation marks.
• 00:53 You could also use single, it doesn't matter at all.
• 00:55 And let's go Tim.
• 00:57 So here we have a list of 1, 2, 3, 4 items.
• 01:02 Now the fun thing about lists are they are numbered.
• 01:05 So each of these things is a number and lists start at zero.
• 01:08 So John is 0, it's the zeroeth with item of our list.
• 01:12 Tina is the first item.
• 01:14 Bob is the second and Tim is the third.
• 01:16 Now that seems a little weird.
• 01:17 Tina is not the first, it's obviously the second item, but
• 01:21 like I said, lists start at 0, so 0,1,2 and 3.
• 01:25 So to access our list, we can do it several ways.
• 01:29 So let's just print our list to the screen.
• 01:31 First off, let's just print out the whole thing.
• 01:32 So print (names).
• 01:34 Let's head back over to our terminal and let's run this.
• 01:38 And we see we get this whole list of things and
• 01:40 the square brackets are there and the quotation marks are all there.
• 01:43 And that's not particularly useful.
• 01:45 So you usually don't just call the entire list when you have a list.
• 01:50 Instead, you call out specific items of that list.
• 01:54 So to do that, we just reference their index number.
• 01:57 And we do that by slapping some square brackets to the end of our variable
• 02:02 name or list name, and just calling out the list item.
• 02:06 So if we want to reference John, that's the zeroth item,
• 02:09 we would just type names and then put a zero in there.
• 02:12 So let's save this and run it, see what that looks like.
• 02:16 And you'll notice it just prints out John.
• 02:18 If we want Tina, Tina is the first item.
• 02:21 So we could save this and run it.
• 02:24 And when we do it prints out Tina.
• 02:27 All right, very cool.
• 02:30 So, lists are super useful.
• 02:32 We're going to use these over and over again.
• 02:34 And think about Excel, there's often rows and columns of information and
• 02:38 data you want to get out.
• 02:40 Sometimes we'll use lists to pull out those items to represent those items.
• 02:44 So we'll grab everything from an Excel spreadsheet and
• 02:47 we'll add it to a list if it makes sense data-wise for that.
• 02:51 So if we have for instance one column of things,
• 02:54 we would pull out every item in that column and put it in a list.
• 02:57 Now, a lot of times Excel data is more complicated than just single items
• 03:01 like this.
• 03:02 So the list isn't as useful but sometimes it is and it's good to know and so
• 03:07 that's the list.
• 03:08 So very quickly before we end this video, we can delete things in our list.
• 03:15 So we can call the delete function, and then we can reference names and
• 03:18 let's say we want to delete John.
• 03:21 That's the zeroth item.
• 03:22 So now if we run this, we should just see Tina, Bob and
• 03:26 Tim because John is being deleted.
• 03:28 So let's save this and run it and see.
• 03:30 And sure enough, Tina, Bob and Tim john is no longer there.
• 03:35 So that's interesting.
• 03:38 Let's get rid of that.
• 03:39 We can change things.
• 03:41 So if we want to change John to something else, we can just call names and then
• 03:46 reference the thing we want to change, and then set it equal to something else.
• 03:51 So we could code James.
• 03:53 So let's go ahead and save this and run it.
• 03:55 And now we see James, Tina, Bob and Tim.
• 03:59 So that's kind of cool.
• 04:02 Now we're putting strings in here.
• 04:04 We could put numbers in here too.
• 04:06 Notice there's no quotation marks.
• 04:07 As I mentioned in the last video, we never put quotation marks around numbers.
• 04:11 So here 0 1 2 3.
• 04:14 So if we referenced the third item,
• 04:18 it will print out 41 hopefully.
• 04:22 Sure enough 41.
• 04:24 So that's cool.
• 04:26 We can put other variables.
• 04:27 We can go first_name = John and then instead of putting it
• 04:33 explicitly like this, we can reference the variable in here.
• 04:39 So now if we print out names first_name, what do you think it'll print out?
• 04:43 Will it print out first_name or will it print out John?
• 04:47 It should print out John.
• 04:50 And there we go.
• 04:51 So we can put words, we can put strings, texts, numbers,
• 04:55 we can put other lists in there.
• 04:56 So let's call this nums and let's go 1,2,3,4.
• 05:01 So here instead of 41, we can put that whole list.
• 05:06 So now this is 0, 1, 2, 3.
• 05:08 If we reference this third item, it should be this whole list.
• 05:14 This is fun.
• 05:14 And you see there's the whole list.
• 05:18 We can then further reference then things inside of this
• 05:21 list if we want by just slapping another set of brackets on here.
• 05:25 And let's say we want the zeroth item which is 1, we could just do it like that.
• 05:31 If we save this and run it, it prints out 1.
• 05:35 So lists are very, very useful.
• 05:37 And like I said, we're probably going to use these quite a bit throughout this
• 05:40 course as we're pulling data out of our Excel spreadsheets.
• 05:43 They're not that complicated, but like I said, very useful and a lot of fun.
• 05:46 So that's all for this video and the next video we'll look at tuples.

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