‫Welcome back.
‫Remember this exercise that we did a few videos ago where we had some list with letters and I wanted
‫you to find the duplicates and return them in a list of duplicates.
‫In our case, we wrote this function with loops.
‫That returned B and N because both b.
‫And MN where duplicates in the list.
‫Now this is going to be a tough one using what you learned about comprehension.
‫Is there a way to do this neater?
‫For example, I want you to say duplicates.
‫Like this.
‫And create.
‫A comprehension in here that returns this exact same answer B and N, so that if I print duplicates
‫just in one line, I can find the duplicates.
‫You can use set comprehension.
‫So you can use list comprehension, dictionary comprehension, whatever you need.
‫Give it a go.
‫Really think about it.
‫You can pause the video because otherwise I'm going to go with the answer.
‫What I'm going to do is let's remove this.
‫And just start here.
‫Now the first thing I want to do is I want to create a list comprehension.
‫What should I do here?
‫Well, first I know that I'm going to create a variable, so let's just call it X.
‫And here I'm not going to modify any of this.
‫I'm just going to keep X the way it is.
‫So X is going to represent A, B, then C, then B, then D, and I'm going to loop over and say for
‫X.
‫In the list.
‫Some list.
‫I want to only add the items that are repeated.
‫So how can I check for that?
‫Well, we can do an if statement.
‫And in here I'm going to say.
‫Well, some list dot count.
‫Remember, Count tells us how many times an item appears in the list.
‫So we just give it the x parameter.
‫So A to let us know, hey, how many times does A appear in the list?
‫How many times does B appear in the list?
‫How many times does C, does B, so on and so forth?
‫And our if statement should check if the number is greater than one.
‫Right.
‫So let's see what happens when I return this if I click Run.
‫Look at that.
‫I get b, b and N.
‫All right, that's good, but.
‫I want to only have them once.
‫I only need B and N.
‫I don't need to know that.
‫Well, I don't need a list of four letters.
‫So how can we do this?
‫We know that we can create a set like this, right?
‫I can say set.
‫And wrap it in here so that the entire list gets turned into a set.
‫So we give this to the set and then what happens?
‫Oh, and this needs to be brackets, right?
‫Because this is a function.
‫So this is the set function that Python gives us.
‫So if I run this.
‫Look at that.
‫I have An and B almost done because well, this is now a set.
‫I asked you to return me a list.
‫So what should we do?
‫Well, we now can create a list out of that set.
‫If I click Run.
‫There we go.
‫We have our duplicates all in one line, mind you, a very long line.
‫And maybe this isn't the most readable code, but that's pretty cool.
‫Now, this is a tough one.
‫Maybe you didn't get it the first time around.
‫It's okay.
‫This is just something that you have to practice.
‫You have to do a bunch of problems and you'll get used to eventually as you progress through your career.
‫But that's it for comprehension.
‫I'll see you in the next video.
‫Bye bye.