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Hello and welcome to this video.

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In this video I will be showing you how to access the elements of a list so you can access the elements

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of values in a list by using the index.

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The index basically refers to the position of the elements in a list with a pint on list.

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The index are zero based.

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What that means.

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The first element or item in the list is given a position of zero.

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So let's take a look at an example.

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So let's look at this list here which is called animals.

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So with this list if we want to access say the bear.

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This will be Position ZERO.

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This would be position 1 and this will be position two.

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So it is a zero based index.

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So let's take a look at how we would do this.

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So I've got some code here from a previous video so I'm going to comment out some lines here.

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So because I don't want them to be printed I want them to be ignored.

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So I just commented out all right.

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So these are all commented out now.

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So if I wanted to access the bay from this list this is how I would do it.

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Type in print and in parentheses I refer to the name of the list.

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So the name is called animals and then inside that are the square bracket and type in a zero.

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So the zero is the index.

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So what that means when this print.

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It will just grab the zero index which is the first item or element in the list which is this code bear.

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So I'm going to save that and if I open up my command prompt and just typing the name of my file which

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is my list dot P Y and press enter and you can see is giving me the value of Bear which is the first

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item on the list.

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Now if I wanted to access the tiger the tiger I will have an index of 1.

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I'll have to replace the 0 with a 1 and so on.

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Depending on how many items you have on the list if you notice because I have commented up blocks of

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my code the bits I have added a comment to it has not been displayed on the screen.

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So comments are quite useful if you want to try different things and you don't want all the code in

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your file to be acted upon.

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So it blocks out the aspects you don't want to be executed or printed on the screen.

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You can also access elements within a list from the back of the list.

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So if you're doing a zero based index it would access the elements from the first.

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Now if I change this from zero to say negative or one minus one what that will do it will access from

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the back of the list it will not give me elephant rather than bed.

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Let's check this out.

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I'm just going to save the file and open up my command prompt and execute.

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You can see now is giving me elephant instead of the bed because I have used a negative when you use

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a negative index.

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It gives you a value from the back of the list.

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Another thing you can do with access in list items is that you can access a range.

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For example I can if I wanted to access save from this to this you can specify that or if you want to

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access if you want to start listing from a set an index you can.

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So this is Position ZERO.

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This is position well let's say I want to just print out anything from position 1 and not 0.

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So the way we do that inside my print statement I would just do one and I'll do a call on what that

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would do it will print out everything apart from the position of zero.

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So let's check that out.

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And I'm just going to type in the name of my file which is my list the p y and press enter and you can

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see it prints out tiger lion pendant elephant but he skips the bear.

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So by using the index number on the colon to print every 10 after that index as you can see here another

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thing you can do is you can specify a range.

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So let's say I only want the tiger and the lion printed on the screen.

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So instead of just doing the one on the column I can come here and add three.

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So this is Position ZERO position one position to position three.

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What this will do it will print just position one position two but it will not print position number

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three.

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So let's save that and check that out.

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Inside Hart terminal all command prompt.

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So I just type in the name of my file which is my list.

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The P Y press printer.

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And as you can see this is just printed out the tiger and the lion the tiger is position one and the

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lion is position 2.

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It doesn't print position 3 so I'm giving it a range.

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So I'll say print grab the values from position 1 and 2.

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All right does what that does on the final thing I want to show you in this video is how to modify the

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lists.

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So if you want to change the item in the list let's say this item called Bear.

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I want to change that to a dog the way I would do that.

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I just type in the name of the list which is animals and how add the square bracket and add the index

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of what I want to change which is the bear.

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He has a index of zero and then I use the equals to sign to set a new value for what I want to change

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it to.

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So let's say I want to change the value of the bear to the dog.

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That's how I would do that.

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So I do control is to save on a Mac.

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You can do command s.

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Now I can test this if I do a print inside that print and type in the name of my list I'm passing the

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index of 0.

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Now this index of 0 will no longer see bear it should now see dog because I have made a modification

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to that name.

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So let's save that.

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Let's go back into my command prompt.

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I type in my list the p y and press enter and as you can see is giving me the value of dog.

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So when you executing code it would do it.

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Line by line.

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So this here is printing out this code here on line 5.

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That's this line and then this print here on May 7 refers to this dog that I am telling it to grab the

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value of that index 0.

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So that's basically how you can play around and access values and also modify values within a list.

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Thanks for watching and bye for now.