‫Welcome back.
‫Let's do an exercise where we check for duplicates in a list.
‫So I have some lists here, and I want you to be able to check this list and print whatever the duplicate
‫values are.
‫In this case, we see that DN has duplicates and also B has duplicates.
‫So I want you to print B and D as a list in here.
‫How would you go about doing that?
‫Pause the video.
‫Give it a go.
‫Otherwise, I'm going to keep going with the answer.
‫And by the way, you're not allowed to use sets for this.
‫So for this exercise, you can use the data structure sets.
‫Instead, you have to just use conditionals and loops that we've learned in the past couple of videos.
‫So give it a try.
‫Pause the video and when you're ready, I'm going to go ahead with the answer.
‫First I'm going to create a variable called duplicates, and this is going to be an empty list that
‫we're going to populate with any duplicate values.
‫Next, I'm going to loop over this list, so I'm going to say four value and some list.
‫And in here.
‫Well.
‫What can we do?
‫This is a tough one.
‫But what I'm going to do is say if some list does not count, remember, count allows us to count how
‫many times an item in a list exists.
‫And I'm going to say value.
‫So that sum list count, and I give it a.
‫It's going to come from me.
‫How many times a day happens in the list?
‫Very, very useful.
‫Again, if you didn't come up with that, there's many solutions to this problem.
‫So there's no one right answer.
‫I'm just showing you how I would have done it.
‫Now, here, I'm going to say if that's greater than one, in that case, that means there's a duplicate.
‫So I'm going to add it inside of the duplicates.
‫So let's just go ahead and say dot append, because I want to append and in here say value.
‫And at the end of all this, let's just print duplicates.
‫Now.
‫Let's see if this works.
‫I'm going to click Run.
‫And.
‫All right, I get both be.
‫And MN.
‫But I don't need this duplicates.
‫I just need to know what are the duplicates?
‫I just need one instance of B in one instance of NW.
‫So what we can do here is do another if statement and say if the value.
‫Is not in duplicate.
‫And yes, this is a bit of a trick.
‫You may remember that knot is the opposite, right?
‫So we're checking.
‫Hey, is value in duplicates?
‫And not essentially says, hey, if value is not in duplicates, it reads like English.
‫And this is going to evaluate to true and false.
‫And then finally make sure that we get the indentation right, we're going to append the value.
‫So if I click Run.
‫I get B and N.
‫Again if he didn't get this right away, don't worry.
‫It can get tricky.
‫And this is one of those things that you just need to keep practicing.
‫But you see here that I was able to use loops, I was able to use logical operators like knot and conditionals,
‫like if statements to solve a problem in just a few lines of code.