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Instructor: Can you believe it?

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I hope I didn't put you to sleep, but we're almost there.

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We have one last main data type, set, and then we're done.

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I know, I know this isn't the most exciting topic.

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Trust me, this is the hardest part.

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When you're starting out

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and you're just learning these things

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without understanding why do I need this,

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how am I gonna build the next game,

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how am I gonna build the next Netflix,

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how am I gonna build the next coolest Apple app,

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you're looking at this and thinking,

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"I just learned a bunch of theory.

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I feel like I'm in math class all over again."

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I know, trust me, I went through this.

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I was a self-taught programmer as well.

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These are the Lego blocks that builds our foundation.

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Once we learn these, we can move on to new things.

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And you'll see that once you climb this little mountain,

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things become so much easier,

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and you'll realize the power

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when we start building these projects

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toward the end of the class where you're gonna say,

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"Oh, all these blocks that we learned,

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all this, frankly, boring part is all going to make sense."

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So hang in there.

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It's supposed to be hard, it's supposed to be tough,

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but you'll see very soon why this is so powerful

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and why what we've just learned is gonna allow us

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to build some really awesome things

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and create some really awesome programs.

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So let's finish off with the last one, the last data type,

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the last data structure that we'll see in Python,

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at least from the main ones, and it's called set.

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And sets are simply unordered collections of unique objects.

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Hmm. Let's have a look.

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Let's create a my_set,

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and my_set we create with curly brackets like a dictionary,

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but instead of a dictionary, we don't have key value pairs.

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Instead, we just have values like 1, 2, 3, 4, 5.

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That's it. That's a set.

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We just created a set.

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But remember the definition I gave you.

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Set is an unordered collection of unique objects.

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What does that mean?

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Well, if I print this

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and say my_set and I click run, I get a set.

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But if I had, let's say, another 5 in here and I click run,

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it only returns the unique sets or unique items.

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You see in a set, there's no duplicates.

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Everything has to be unique.

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So this 5 just never gets added to a set.

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For example, you can add things to a set, like my_set,

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and then I can say .add and give it a value, like 100.

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And then let's say I do my_set.add and then give it 2.

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If I click run here, I see that I was able to add 100,

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but 2, well, 2 wasn't really added

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because my_set already contained that data.

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It's unordered.

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I mean, we've created 1, 2, 3, 4, 5 here,

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but there's no real order to it.

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There's no bookshelf

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in our memory space that is right next to each other.

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These are all over the place in memory,

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but a set is able to find them because they're all unique.

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So they're all in just one location in memory.

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So let me ask you this,

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and this is gonna be a fun little exercise.

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If I gave you an array,

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and let's say this array contained, well, this right here,

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and I want you to return an array with no duplicates.

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So I want everything in, let's say, let's call it my_list,

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and a programmer has already created this.

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Okay, and then your task is to create

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or return a list or a collection that has only unique items.

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How would you go about converting this into a set?

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Well, we've seen this before.

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We have a set function,

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and we simply wrap my_list in that set,

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and let's print it out.

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I click run. Check it out.

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We have formed a new set from a list,

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and I've removed all duplicate values.

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When would this be useful?

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Imagine if we had usernames, right, or email addresses.

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We're collecting email addresses on our startup page,

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but we don't wanna have duplicate emails.

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We might wanna convert this, a list of emails, to a set

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and remove any duplicates

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so we're not sending emails over and over.

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So that's really cool.

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What about this?

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Can I, let's change this into a set.

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So let's call it my_set.

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Going to change this into a set. There you go.

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And then what if I wanted to access my_set at index of 0?

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Hmm. Set object does not support indexing.

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Well, again, you can think of it more as a dictionary.

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In order to access a set,

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we have to grab by the item that's in it.

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That's the key to getting the information from memory.

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The way we would check

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if something exists is we simply say,

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"Hey, is 1 in my_set?"

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And we run this, and we get True.

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We can also do length of my_set and we get 5.

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Again, nothing too crazy, but 1, 2, 3, 4, 5.

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Remember, it only counts the unique things

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because this will never gets entered.

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It's a set.

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And alternatively, we can also convert this into a list.

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If I click run here,

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you'll see that I now have my_set as a list.

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And then we can also do, let's say,

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my_set.copy and actually copy my_set into something,

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let's say, new or new_set.

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And then this will be completely different or a new copy

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then this original one.

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So let's test this out. This new_set.

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If I use a method that we may have seen before,

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which is my_set.clear,

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which, as you can imagine, clears the set,

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and I click run, I have that new set,

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but when I try and print our all set, which was my_set,

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it's going to be empty, an empty set.

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But the true power of sets

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comes in the next couple of methods

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that I'm going to show you.

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And sets have quite a few methods.

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But don't worry, most of them are quite similar.

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So let's explore that in the next video.