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-: All right, let's learn about some actions

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that we can take on lists.

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And this is very exciting

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because you can perform a lot of actions on lists.

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Now, we've learned about built-in functions, right?

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Functions that come with Python

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and we've actually seen this one before

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when we talked about strings,

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which is the length function.

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And here we can have it calculate the length of a list.

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So for example if we had a basket here

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that had 1, 2, 3, 4, 5.

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Well this basket, if I calculate the length of a basket

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let's do print here so we can see the result.

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And I click run,

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I get...

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five.

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The length of the basket is five

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because well, there's five items.

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Remember a length is the actual length.

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It doesn't start counting from zero.

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It's gonna do human length, which is five.

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But lists get really powerful when it comes to methods.

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So instead of a built-in function,

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remember a method is an action

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that's owned by something

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and it's specific, let's say, to a data type.

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So if we go to list methods,

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you'll see that Python has a few list methods

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that we can use.

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And the way we use these methods

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is remember we just add a dot

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after a list.

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So let's have a look at some of them.

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First, I'm going to start off with the adding ones.

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So let's say in this basket

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we wanna add something to it, to the end of the list.

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Well, we can use the append and remember, with a method

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as soon as you write the dot

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it'll tell you what we can use,

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which is very very useful when you have an editor.

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So the first one is append.

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And if I hover over this,

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well it just tells me append an object to end.

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And in Python, an object is,

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well everything in Python is an object.

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A number is an object.

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A list is an object.

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So just think of it as an item for now.

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So if I wanna append

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let's say 100 to the end of the list, and you know what?

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Let's add a new list here.

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And this new list, we'll do the append for us.

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If I print the new list and I click run,

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I get none.

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Hmm, that's weird.

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What if I print

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basket here?

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If I click run?

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All right, so it looks like

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the basket was appended to,

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we added a hundred but a new list,

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when we assigned it,

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the basket dot append, that new list is completely none.

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And that is because append changes the list

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in place.

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What does in place mean?

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It means that it doesn't produce a value.

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All it does is saying, Hey

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I'm just going to append a hundred

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to this basket that you gave me, but I don't really care.

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I'm not producing a result.

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I'm just changing this for you.

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I know it's a little confusing.

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So in order for our new list

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to have that a hundred at the end,

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we have to do something like this.

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If I click run,

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there we go.

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After we've appended to the basket, then we can assign.

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So that new list points to basket

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which points to this list that was modified.

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All right, what else is there?

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Well, there's also something called insert.

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And you see over here that insert

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gives an index and an object.

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So we can insert something not at the end of the list.

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I mean, we could but we can also insert it

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anywhere we want in an index.

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So for example, in this case, if I do insert a hundred

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at 0 1, 2, 3, 4, so let's do index of four,

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and I click run.

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I've added a hundred to the index of four.

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If I do index of five and I click run

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I've added a hundred at the end of the list.

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Now let's try and copy this

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and see if we can just add it into here.

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If I click run,

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again, same thing.

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Insert modifies the list in place.

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It doesn't create a new copy of the list.

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All right?

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And if we add this, like this,

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well once again insert modifies

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the list in place.

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That is, it doesn't really output a new list.

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It just modifies whatever is existing in memory.

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Finally, there is another method called Extend.

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An Extend instead of an actual item or object

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takes what we call an iterable,

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which we're gonna get into later on

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but it's something that you can loop over,

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you can iterate over, which is a list.

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So we just give it another list,

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like let's say a hundred or 101.

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So if I run this, once again, it doesn't output a new list

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it just modifies the list in place and adds on

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or extends our list.

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And we can also just give it one item.

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All right, let's keep going with the removing methods.

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Now, with the removing, we once again

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have a few fun things that we can do.

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So let's continue with this basket

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that we've been using that now has

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a hundred included into it.

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And the way we can remove things is,

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well there's a few ways.

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First one is basket dot pop.

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And basket dot pop,

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If I go like this,

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and let's print this basket.

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I'm going to comment out the new list for now

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since we're not using it.

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And then we're going to say, basket dot pop,

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and then print...

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basket.

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Let's run this

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and pop pops off whatever is at the end of the list.

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In our case, at the end of the list,

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because we've extended the basket to a hundred,

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that a hundred gets removed.

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If I do basket dot pop again,

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whoop, not here, down here,

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and I run, you see that both 100 and 5 get removed.

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What if I do pop zero?

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If I click run here,

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it removes the item

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in the index.

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So here, pop zero is going to remove

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whatever's at index of zero, which is one.

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Now, there's also dot, remove.

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Remove, again, is, we give it a value

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that we wanna remove.

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So in our case, let's say we wanna remove number four.

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Well, if we run this,

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it's going to remove four for us.

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So remove, we give it the value that we wanna remove.

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With pop, we give it the index that we wanna remove.

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And just to see if this is working

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let's add a new list here,

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and we'll say new list

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equals basket dot remove.

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Add a new list here.

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See if that gets modified.

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Nope, it does not get modified.

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That means remove is working in place.

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It doesn't return a value, it just simply changes

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whatever list you give it.

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What if we do pop?

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If I run this,

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I get five.

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Hmm,

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why is that?

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And this is something that you just have to get used to.

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Different methods do different things.

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For example, pop, the way it works

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is that pop returns

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whatever you have just removed.

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In our case, when we did four

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that is index of 0, 1, 2, 3, 4.

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It returned the number five for me.

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Even though it removed it from the basket

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it still returned something.

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And the reason for others is that we got none.

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That is when a method doesn't return anything,

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it returns none, a topic we're gonna cover shortly.

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So you have to be careful

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and understand what each method returns.

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If I go over extend,

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I see here that this little arrow

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shows me that none is returned.

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That means it's not going to produce anything

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with this method.

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It's only going to change

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or extend a list that it was given.

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Don't worry if this is confusing.

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That's something that you're gonna get used to

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as we get more and more practice.

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Now, the last removing method I wanna show you

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is clear

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And clear, as you might guess.

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If I click run here,

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well, this is none

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but if I go to basket and I click run,

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the basket is empty.

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Clear removes whatever's in the list.

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Completely clears it just as a name suggests.

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All right, that was a lot, but there's still a few more.

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So let's take a break

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and then I'll see you in the next video.

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Bye-bye.