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Instructor: Welcome back.

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Let's talk about our next data type,

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and it's a big one, a very, very useful one.

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It's called list.

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And list is an ordered sequence of objects

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that can be of any type.

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So you can think of them as strings, right?

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We had strings previously that we learned about,

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except that each sequence of this string,

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well, was a string, was a letter

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or a number wrapped in quotation marks.

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Lists, on the other hand, looks something like this.

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Let's say we create a variable, li,

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and lists we denote with square brackets,

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and inside of these square brackets,

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we can have different objects.

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So for example, we can have 1, 2, 3, 4, 5.

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We can also have, let's say li2,

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and this is going to have a, b, c,

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and it can have any collection of items that we want.

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We can even mix and match,

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and say that we have one, two, then a,

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then maybe even the Boolean value true.

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So all of these are lists.

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Now, lists are extremely important,

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and in other programming languages

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you might have heard the word arrays.

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So in Python, lists are a form of array,

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and later on when we get into the modules section

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of the course, we will talk about the difference

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between lists and arrays.

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But if you are coming

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from a different programming background,

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then lists are like arrays in your language,

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a collection of items.

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Now, the neat thing about lists is

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that it's the first data structure that we're learning.

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Now, what is a data structure?

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Data structure is a very important concept

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in programming languages.

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It's a way for us to organize information and data

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into, let's say, a folder or a cupboard or a box,

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so that these data structures can be used

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with different pros and cons.

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For example, you have a fridge where you store your food,

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and fridges are really, really good

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at putting your food inside, keeping it cold,

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and then taking it out.

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Or you might have a backpack.

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A backpack is really really good

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to stuff everything in there.

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But when you're looking for things in a backpack,

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it's really, really hard.

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So you can think of data structures as similar to that,

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a container around your data

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that has different pros and cons

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of accessing that data, removing that data, writing data.

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But that's something we'll get into a little bit later.

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The key here is that these square brackets

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allow us to contain information and data,

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like strings, integers, floats, if we want to

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Booleans, into a contained fashion.

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So let's think of a good example here.

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What if we had a shopping cart?

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Let's say we're Amazon here,

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and then Amazon has the Amazon shopping cart,

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and in here we can collect different things that we want.

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Maybe we collect some, I don't know, notebooks

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And you know what?

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Let's get some gadgets.

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Let's get some, maybe some sunglasses.

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We can add different items here, different strings,

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different data into this cart.

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And now, just like we saw in strings,

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we can access the Amazon cart in different ways.

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For example, I can access it, again,

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with square brackets and simply say, I want item zero.

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So if I print here,

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and do amazon_cart,

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look at that, I get notebooks.

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The second item,

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I get sunglasses.

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What about the third item?

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Nope, list index out of range.

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But this should make sense now.

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This is a list where we're accessing the index of,

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but it only contains two items.

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So if we're going zero, 1, 2,

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the third item, nothing exists.

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So our program says that doesn't work.

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You're doing something wrong.

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And just like strings, these list items are in memory

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in their separate bookshelf, right?

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But one right next to each other.

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So we can go 0, 1, 2, 3, 4, 5,

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so on and so forth until the list ends.

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All right, let's learn about lists a lot more

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in the next video, bye-bye.