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-: Welcome back.

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Let's talk about some useful tricks

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with lists that you'll see a lot in Python code.

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Well, one we have already seen, it's this idea of length.

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You're gonna be using this a lot.

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That is to figure out the length of a list

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which in our case is now seven.

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Another really useful trick is to reverse a list.

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Now, I've already showed you how to reverse a list

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but sometimes you can do that with list slicing.

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Again, something that we've seen in string slicing

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so I can actually do basket

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and then semicolon, semicolon, negative one.

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If I click run here, is that what you expected?

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Let's go through this line by line.

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I've sorted the basket so that it's from A all the way to Z

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and then I've reversed this, so it's in Z all the way to A

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and then I've reversed the basket again, so that instead

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of being in reverse, it's now in order A, B, C, D, E, X.

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And this list slicing creates a new list, right?

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If I print

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basket here

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you'll see that the basket is the reversed version

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the last action that we've taken on it

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versus list slicing that creates a new version.

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So this notation, you'll see a lot

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with lists when you need to reverse a list

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or maybe you need to make a copy of the list like this

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or maybe you need a portion of the list.

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Another useful thing that you'll see a lot of

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is something called range.

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Let's comment this out for now.

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If I wanted to generate a list really quickly, let's say

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from one to a hundred, I can do something like this.

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I can say range, and then start, and then stop.

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So, let's do a hundred,

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and if I print this

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and I run, hmm,

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I get a range one to a hundred.

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But if I wrap this in a list, which is going to

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create a new list for us, and I click run,

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look at that.

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I get a range from one all the way to 99.

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Remember, it's the start and then whatever to stop at.

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So before it hits a hundred, it's going to stop.

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Now, if I remove this and just do one single thing

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I get a list starting from zero all the way to 99.

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If I want a list that has 101 items, because it starts

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at zero, I would just do 101.

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And range is something we'll talk about a lot more

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especially when we talk about loops in programming.

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But this is a great way of you to generate a list really

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really quickly, especially a numbered list.

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Finally, the last common thing that you'll see a lot

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is this idea of dot join.

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What is dot join?

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Join is actually something that works on strings.

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It's a string method, but it's often used this way.

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We have an empty string and this empty string

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let's say sentence, and then we can do sentence dot, join

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and join takes what we call an iterable,

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which is a list for now.

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And in here we can have a sentence like,

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"Hi, my name is Jojo."

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And now if I print the sentence

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and I click run here, hmm, I don't get anything.

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Let's figure out why.

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What if I type in an exclamation mark here and I click run?

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All right, it's printing out sentence, but it looks

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like dot join creates a new item for us.

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So let's just assign that to new sentence.

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Now, if I do new sentence and print that out

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we see that I get, Hi, my name is Jojo.

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Hmm. So this is a little funky, right?

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We have these exclamation marks between our items

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and join joins these little iterable items

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these lists by whatever is in front of it.

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So if we actually change this

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to an empty string, click run, we now get this.

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If I add a space in between and click run,

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we get, Hi, my name is Jojo.

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And sometimes you'll notice this pattern a lot

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especially if you wanna join

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and create a new string out of a list of items.

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Now, a shorthand way

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of doing this is to actually not even bother with this

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and just doing an empty string dot join

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and then joining all the list items.

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There we go.

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So all we are doing is combining lists into a string

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and this is a common pattern that you'll see a lot of.

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I'll see in the next one.

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Bye-bye.