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Welcome back in this video, we're going to look at lists and this can be used to hold both single data

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types and custom objects or classes that can be resized to grow as new values are added.

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The immutable types which can be written to and there are immutable types that you cannot write into

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but only read from.

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And let's look at those.

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So first of all, let's create a list of months, so well, months, which will be a list of you just

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used this method here and then you add the elements.

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So for example, January, then February, and then, for example, March and so forth.

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OK, I'm not going to go over all of the months.

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The cool thing of list of that, it can contain any type of list item.

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So while any types, for example, is going to be a list of and then you have a number, well, a bunch

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of numbers here.

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So one, two three and then you have the Boolean value, true or false, and then you have the string,

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you know, like it's accepts all types of data.

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So in order to print the amount of items that you have in an item, you can just go ahead and use print

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any types thought size.

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So let's run this and actually see something in action.

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And this will just tell me that there are six items in here, so one, two, three, four, five and

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six.

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Can also access items off a given list by using the index, so for example, if I want to get February,

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I would use months with the index of one.

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And let me comment this line out here and run it again.

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And now it will say February.

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You can also look through it in a similar fashion, as we've seen before.

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Right.

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So you have a follow-up with the month in months and then you just print each month in a new line with

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the month like so.

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OK, so let's check that out, comment this line out here and get all of the months that we have in

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there.

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So January, February, March.

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OK, so now let's look at what we can do with such a list of list.

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OK, so we can just go ahead and use months dot and then see what our I.D. offers us.

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And you can see it has a bunch of methods to offer.

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Well, it doesn't allow me to do it properly now.

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It's complaining because of the errors that we're creating here.

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But you can see that there are a bunch of methods that you can use from.

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It's going to allow you to select one of those.

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In my case, my I.D. just doesn't seem to like it right now.

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But generally speaking, you can just go ahead and check.

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So here, for example, with any types thought and you can see list index of, then we have the list

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iterator size.

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So it has a bunch of properties as well as methods that we can use, and you could just play around

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with those if you want to.

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Now the problem here is that these lists are immutable, so we cannot add new items to them.

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Of course, when we changed to code here, but we cannot add a new item to months, for example.

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So, for example, there is no add method here, so we cannot and new items to it.

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And in order to make a list that is going to be immutable, we can convert our existing list into a

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mutable list and then add items.

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So let's convert months into an additional month's list, and we're going to use month start to mutable

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list like so and all this additional months is going to be a list now, which will be a list, but it

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will be changeable so we can add new items to it.

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So let's create a new month's list, which will in this case, be an array of.

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And I'm just going to add April, then I'm going to add May and June, for example.

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Right now, what I can do is I can combine them so I can use additional months start at all.

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So I want to add all items from my new month's array.

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OK, and now let's print the additional months.

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Like, so let's see what's going to be displayed for us.

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I could see January, February, March, April, May, June.

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So we added those months and that worked.

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So the month itself will only have two or three months in them.

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But then we have this additional months list, which is a mutable list that we can mutate, meaning

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we can change.

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Now, if you want not to add all the months at once and you don't want to create a separate array off

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or whatever, you can just go ahead and use additional months to add and you can add, for example,

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July here.

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OK, let's run the code again, and this will now add another month to our list.

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You can see here so you can use it as a little challenge to add the other months that are still missing.

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So positive VIDEO And at the other, either with this approach or with the approach that you saw earlier

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with the array of different months.

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Now, if you want to create a mutable list of a particular type, you can also go ahead and just say

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mutable list off.

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And then you need to define the type.

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So here I'm going to find that it's going to be a type of string and here I have two different days.

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So for example, Monday, Tuesday, Wednesday, OK.

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And now we can add to our days because it's a mutable list, right?

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We can use, add and had the first day to it and then, for example, printed days like so.

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And let me not print that anymore.

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Let's run it through a quick here.

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And we can see it, Prince did this for us.

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So that's how you add items.

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What if you want to override items in a given list?

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Well, you can just go ahead and say that at the position of days two, for example, which would be

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Wednesday.

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I'm just going to change that to Sunday.

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And now that's right, again.

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You can see now we have Monday, Tuesday, Sunday, Thursday.

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And now, if you want to remove a given item, you can just use to remove, add method, so remove that

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and then you need to pass the index, or you could remove all items, or you could remove a filter of

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items and so forth.

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But we're going to keep it simple.

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Let's say I want to remove the item at Index three, which in this case would be thirsty.

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So let's run again.

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And we can see it's just as Monday, Tuesday as Sunday, so this first day that I added earlier now

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was deleted.

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So now instead, let's delete index one, which will delete the Tuesday from it.

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So Monday, Sunday, Thursday.

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OK.

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That is how you can remove a particular item.

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But if you want to remove all.

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Well, you can just go ahead and say they start, remove all.

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And here you need to say which kind of list you want to remove.

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So let's say you just want to remove a filter of it.

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You can create.

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Another list will remove list, and this will be able to move the list or however you want to call it,

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this will be a mutable list of strengths as well, but it will just contain money and wood.

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OK, so now you could go ahead and only remove particular items by reusing the remove list like so and

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run it again.

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And you will see that Monday and Wednesday are not going to be a part of the list anymore.

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So Tuesday, Sunday, Thursday, because we deleted the other list that we created.

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But you can also just use days, which is also a mutable list, right?

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So here let me do the same thing with day start.

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Remove all, and here I'm just going to pass this.

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This will remove all of the items.

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So you see print dates, just give me an empty list.

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So that's really how you can delete the entire thing.

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Basically, you are passing the filter that you want to apply.

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I am passing all day, said I want to delete, so it just removes all for me.

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So I would really recommend to just go ahead and use the DOT operator to then just get some ideas of

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what you can do with it.

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You know, you can replace all you can add and so forth.

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There are a bunch of items that you have there, like you have.

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You can get the size, you can set things and so forth.

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Just play around with the methods there and you should be good.