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Hey friends, welcome back to our Python
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for beginners series. Well, this s Raja
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Lakmi Singum and today's program is a
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short one, but it's packed with an
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important lesson and we are going to
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learn how to replace the first element
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of a list, but only if it's negative. It
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sounds easy, right? But here is the cool
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part. This tiny idea will teach you how
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to check conditions and update lists at
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the same time. So just imagine the user
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will enter a list of numbers and we'll
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check if the list is not empty and then
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if the first element is negative, we'll
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replace it with a zero and finally we
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will print the modified list.
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Okay, let's start coding together. So
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dot split and you'll use comma to split.
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So if my list so if it's not empty if
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here is the step three.
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Check if the first element is negative
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So if to access the first element we
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have index concept we have already
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learned how to access the elements in
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this list using the index concept. So
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I'm doing the same thing. So if in if if
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of zero is nothing but you're accessing
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the first element and it's less than
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but if you observe I didn't use any
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integers here right I just use the input
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that means the input that I'm getting
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from the user will be in strings so
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it'll be something like like this.
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something like this but I want it to be
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converted to integer so I will add int
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So you can use int anywhere. So I'm
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using it here to convert the first
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element to this integer from string. So
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then what you will do if the number is
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less than zero that means if the number
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is negative then you will just simply
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And that's it. It's as simple as that.
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But always remember that you that the
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list is actually a string list. So I
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just want you to replace it with a
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string to zero. That's it. And then you
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don't have to write else. I know every
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if part should have else. I even I told
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it in the previous videos. But if you
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really don't need else part, then you
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So then you can just print
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And yeah, let's check. So like for
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example, when we run this, enter the
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numbers separated by commas. So I'm
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So it is actually changing the minus one
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So what's happening here? First we ask
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the user to enter the number separated
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by commas. So like for example if they
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give any - 5, 10 or 20 then after
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splitting it to like this something like
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Next we check if the list is empty or
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not. For that you just do simply my
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list. If there is something then it will
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be true. If the list is empty then it
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will be false. So if it is true then it
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will go here and then it will check
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whether the first element is negative or
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not. So we look at the first element
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which is my list of zero we consider it
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as first element and we'll check how we
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check by doing it less than zero. So if
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it is less than zero then we consider it
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as negative. So but in order to check we
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also have to convert this string to an
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integer. So that's why I'm using int
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here. So now the first it will take
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minus5 which is in string and then it'll
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be converted to integer minus 5 and then
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it will check whether it is less than
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zero or not. If it is less than zero
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then it will simply change the first
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So finally we print the modified list.
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Now let's try again with the list that
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doesn't start with negative
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30. The modified list is 15 25 30.
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Nothing changed because the first number
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was already positive. So it will come
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here. it will check whether the list is
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there or not. If the list is there then
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it will check whether the number is less
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than zero or not. So if the number is if
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this condition is false that means if
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the number is greater than zero then
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simply it will skip this else part. It
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will come out of it and then it will
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And there you go. You just learned how
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to check the first element of a list and
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update it if needed. This may look
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small, but trust me, you will use this
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kind of logic again and again in bigger
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projects. All right, before we wrap up,
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let me ask you something. If this video
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helped you learn even a little bit,
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isn't that worth a tiny thank you? And
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the best way you can thank me is by
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hitting the subscribe button. Think of
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it like adding yourself to the Python
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learners list, except this time there's
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no negative numbers, only positive
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vibes. So go ahead, subscribe, ring the
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bell icon, and let's keep learning
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Python together. Until next time, keep
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coding and keep smiling. See you soon.
