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Let's continue with lists now.

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So far, the square brackets, we've seen them before, right?

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We saw them when working with strings and just like strings lists are quite similar in that we can use

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list slicing.

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If you remember, with string slicing, we had things like hello and we were able to assign into a string,

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let's say a variable string, and we could do a string and then slice.

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So do something like this.

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Where we had the start, the stop and then the step through so that we started index of zero and end

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at index of two.

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And then go one by one, so list slicing is also available to us, so let's make this cart a little

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bit bigger and you can actually just make things cleaner by formatting it this way.

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All right, so what should we add to our cart?

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We'll also add some toys and then you know what, Amazon does groceries now.

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So let's add some delicious grapes.

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Awesome.

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Now, let's say I wanted to get every single item in the cart while we just simply do this.

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And we have our entire list, but let's use some list slicing, let's say I wanted to grab from the

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first item to the second item if I click run.

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I get notebooks and sunglasses.

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Maybe I want to go all the way till the end, but skip every second one.

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I get notebooks and toys.

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We started zero.

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We step over to toys and we step over and we're done.

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Awesome.

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And this is something that we've already seen when talking with strings.

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OK, but here is where it gets interesting.

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Remember how I said that strings are immutable.

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That means we can't change them.

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Right.

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And we talked about this when we had a string like hello, I couldn't do gret zero equals to, let's

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say Z.

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I'd get an error here.

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I get SDR object does not support item assignment.

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It's immutable.

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But the interesting thing with lists is that they are mutable.

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So that if I change my Amazon cart.

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And say that, you know what, I don't really want notebook's so I'm going to grab the first item,

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which is notebook's and instead of notebook's I what do we want?

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We'll say we want a new laptop.

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It's a big upgrade.

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When I print this Amazon cart.

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Look at that, I'm able to change this list.

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And it didn't give me an air in that sense, lists are immutable, we simply replace on the memory bookshelf

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of our computer notebooks and I say, hey, change it to laptop, and they let us do that.

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OK, so that's awesome.

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But let's try something here.

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What if I create another print here and in the Amazon cart, I'll use list slicing to let's say I want

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item from index of one all the way until index of three.

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Let's run this and see what happens.

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Try and guess.

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Is that what you expected?

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Let's go through this code when we get to line ten, we grab the Amazon cart, which has been updated

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with laptop and I grab item one.

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Two, three, so that is sunglasses.

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To toys, so zero one two, and then we stop at three.

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Just to make this easier to understand, let's start off with zero here.

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So that we see that laptop has been changed.

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And then here in the second one, on line 11, we print the Amazon cart.

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But hold on a second, this list did not change, and that is because with list slicing, we're creating

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a new list, a new copy of this list.

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So here we're creating an entirely new list so that I could actually assign it to a variable.

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New cart is going to be Amazon cart.

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And let's just do the same thing here.

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And New Kaat is an entirely new list on its own, I could change new card, let's say zero into, let's

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say gum.

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And if I print this.

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You see that I have two new separate lists, but a list is mutable because I can change whatever is

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at the index any time I want, and every time we do list slicing, we create a new copy of that list.

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But I have a tricky question for you here, what happens if I just do this?

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If I run this.

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Instead of slicing my list, I simply said that new card is going to equal the Amazon cart.

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And I changed a new KAAT index of zero to equal to Gump, but now my Amazon cart got modified as well.

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Why is that?

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And this is a bit of a tricky question that you might encounter in an interview.

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The reason is that right now, the way that I did equals means that, hey, new card is going to equal

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Amazon card.

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And what does Amazon cart equal to?

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Well, Amazon cart points somewhere in memory in our machines that says, hey, this is what Amazon

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cart is.

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So because here we're not copying the list.

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Instead, we're just saying, hey, the value of new card is whatever is in the memory of Amazon cart.

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We now, when we modify Nikhat, are simply changing the Amazon cart all the way back from here.

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So this is an important concept.

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If you want to, let's say, copy a list, then you do something like this.

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Where you copied the entire list and this is something that you'll see a lot in code bases.

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But this line is saying, hey, I want to create a copy use list slicing to copy this Amazon cart and

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it's going to equal new cart so that now if I run this.

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You'll see that the original Amazon cart stays the same, but the new cart is now something different.

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This is a quick gotcha.

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They just have to get used to, but it's an important concept, this idea of copying versus modifying

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the list, and it's something we'll explore a little bit more in the next couple of videos.

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For now, take a break and I'll see in the next one.

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Bye.