‫All right.
‫Let's learn about some actions that we can take on lists.
‫And this is very exciting because you can perform a lot of actions on lists.
‫Now, we've learned about built in functions, right?
‫Functions that come with Python.
‫And we've actually seen this one before when we talked about strengths, which is the length function.
‫And here we can have it calculate the length of a list.
‫So, for example, if we had a basket here that had one, two, three, four, five.
‫Well, this basket.
‫If I calculate the length of the basket, let's do print here so we can see the result.
‫And I click Run.
‫I get.
‫The length of the basket is five because while there's five items, remember a length is the actual
‫length.
‫It doesn't start counting from zero.
‫It's going to do human length, which is five.
‫But lists get really powerful when it comes to methods.
‫So instead of a built in function, remember, a method is a nice action that it's owned by something
‫and it's specific, let's say, to a data type.
‫So if we go to list methods, you'll see that Python has a few list methods that we can use.
‫And the way we use these methods is remember, we just add a dot after a list.
‫So let's have a look at some of them.
‫First, I'm going to start off with the adding ones.
‫So let's say in this basket, we want to add something to it to the end of the list.
‫Well, we can use the append and remember with a method.
‫As soon as you write the dot, I'll tell you what we can use, which is very, very useful when you
‫have an editor.
‫So the first one is a pen.
‫And if I hover over this, well, it just tells me a pen is an object to end.
‫And in Python, an object is.
‫Well, everything in Python is an object.
‫A number is an object.
‫A list is an object.
‫So just think of it as an item for now.
‫So if I want to append, let's say 100 to the end of the list.
‫And you know what, let's add a new list here, and this new list will do the append for us.
‫If I print the new list and I click Run.
‫I get none.
‫Hmm.
‫That's weird.
‫What if I print?
‫Basket here.
‫If I click Run.
‫All right.
‫So it looks like.
‫The basket was appended to we added 100 but a new list when we assigned it.
‫The basket append.
‫That new list is completely none and that is because append changes the list in place.
‫What does in-place mean?
‫It means that it doesn't produce a value.
‫All it does is saying, Hey, I'm just going to append 100 to this basket that you gave me, but I don't
‫really care.
‫I'm not producing a result.
‫I'm just changing this for you.
‫I know it's a little confusing.
‫So in order for our new list to have that 100 at the end, we have to do something like this.
‫If I click Run.
‫There we go.
‫After we've appended.
‫To the basket, then we can assign so that new list points to basket, which points to this list that
‫was modified.
‫All right.
‫What else is there?
‫Well, there's also something called insert.
‫And you see over here that insert gives an index and an object so we can insert something not at the
‫end of the list.
‫I mean, we could, but we can also insert it anywhere we want in an index.
‫So for example, in this case, if I do insert a 100.
‫At zero one, two, three, four.
‫So let's do index of four and I click run.
‫I've added 100 to the index of four.
‫If I do index of five and I click Run.
‫I've added 100 at the end of the list.
‫Now, let's try and copy this and see if we can just add it into here.
‫If I click Run.
‫Again.
‫Same thing.
‫Insert modifies the list in place.
‫It doesn't create a new copy of the list.
‫All right.
‫And if we add this.
‫Like this.
‫Well.
‫Once again insert modifies the list in place that is.
‫It doesn't really output a new list.
‫It just modifies whatever is existing in memory.
‫Finally, there is another method called extend.
‫An extend instead of an actual item or object takes what we call an iterable, which we're going to
‫get into later on.
‫But it's something that you can loop over, you can iterate over, which is a list.
‫So we just give it another list like let's say 100 or 101.
‫So if I run this once again, it doesn't output a new list.
‫It just modifies the list in place and adds on.
‫Or extends our list.
‫And we can also just give it one item.
‫All right, let's keep going with the removing methods.
‫Now with the removing, we once again have a few fun things that we can do.
‫So let's continue with this basket that we've been using that now has 100 included into it.
‫And the way we can remove things is, well, there's a few ways.
‫First one is basket dot pop.
‫And Basketball Pop.
‫If I go like this and let's print this basket, I'm going to comment out the new list for now since
‫we're not using it.
‫And then we're going to say basket, dot, pop and then print.
‫Basket.
‫Let's run this.
‫And Pop Pop's off whatever is at the end of the list.
‫In our case at the end of the list, because we've extended the basket to 100.
‫That 100 gets removed.
‫If I do basket dot pop again.
‫Oop.
‫Not here.
‫Down here.
‫And I run.
‫You see that both 105 get removed?
‫What if I do pop zero?
‫Five Click Run here.
‫It removes the item.
‫In the index.
‫So here, Pop zero is going to remove whatever is that index of zero, which is one.
‫Now there's also dot remove.
‫Remove again is we give it a value that we want to remove.
‫So in our case, let's say we want to remove number four.
‫Well, if we run this.
‫It's going to remove four for us.
‫So remove we give it the value that we want to remove with pop.
‫We give it the index that we want to remove.
‫And just to see if this is working, let's add a new list here.
‫And we'll say new list equals basket remove.
‫Add a new list here, see if that gets modified.
‫No, it does not get modified.
‫That means remove is working in place.
‫It doesn't return a value.
‫It just simply changes whatever list you give it.
‫What if we do, Pop?
‫If I run this, I get five.
‫Hmm.
‫Why is that?
‫And this is something that you just have to get used to.
‫Different methods do different things.
‫For example, pop.
‫The way it works is that pop returns whatever you have just removed.
‫In our case, when we did four, that is index of zero one, two, three, four it return the number
‫five for me.
‫Even though it removed it from the basket, it still returned something.
‫And the reason for others is that we got none.
‫That is when a method doesn't return anything, it returns none.
‫A topic we're going to cover shortly.
‫So you have to be careful and understand what each method returns.
‫If I go over extend.
‫I see here that this little arrow shows me that none is returned.
‫That means it's not going to produce anything with this method.
‫It's only going to change or extend a list that it was given.
‫Don't worry if this is confusing, that's something that you're going to get used to as we get more
‫and more practice.
‫Now, the last removing method I want to show you is clear and clear.
‫As you might guess, if I click run here.
‫Well, this is none.
‫But if I go to Basket and I click Run.
‫The basket is empty.
‫Clear removes whatever is in the list.
‫Completely clears it.
‫Just as a name suggests.
‫All right.
‫That was a lot, but there's still a few more.
‫So let's take a break and I'll see you in the next video.
‫Bye bye.