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Hey guys, welcome back to this channel.
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If you're new, then welcome to this
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channel. And if you're just joining, you
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are at the right time because today's
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video is short, simple, and super useful
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because we are writing a Python program
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to calculate the area of a circle using
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the radius entered by the user. Sounds
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easy. That's because it is. But there
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are a couple of small things we need to
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talk about like how to use pi and how to
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convert input to numbers and how to
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avoid common beginner mistakes. And also
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I've made a few more exercises before
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this episode as well. If you want to go
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through that as well, I would love to
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encourage you to go there and check the
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basics as well. I have videos on the
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basics as well. And these exercises are
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actually as part of those particular
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series because once you're handy with
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these basics then we can move on to you
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know more complex stuff yet that can be
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easy for you to understand.
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So let's start with the flowchart and
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here you will start always and uh here
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we need radius. We have to take radius
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as input from the user and then we will
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use this formula which is pi into r into
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r and then we have to show the output
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area and then we'll stop.
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So in simple terms the user types the
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radius and python calculates the area
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using the formula and then we'll display
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the result. But before we jump into code
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let's talk about a few key things. So
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the formula to calculate the area of
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So that means you take the radius and
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multiply it by itself. So that's you
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know it's something like a squared part.
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So multiply that result by pi which is
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this one. Now in Python we can write r
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into r to get the square of a number or
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you can also use exponentiation that we
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have used which is where you'll have
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double multiplications at the same time.
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So both will work but wait where does
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you know pi come from? How do how can we
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So you have got two options. One is
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hardcode it manually something like by
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giving pi equal to 3.14159
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or you can let Python give you a super
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accurate version for the math module
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like it will just work for mathematical
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calculations. So we also have that
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Python version. So all you have to do is
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you have to you have to import this
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math. You don't have to worry from where
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it's coming. You just have to write this
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line called import math and then you can
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just give pi equal to math dot pi
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and then it'll it'll get the exact value
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of pi or you can just give something
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which is you know the actual number pi
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Okay. So personally I like using math.pi
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because it's cleaner, more precise and
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easy to remember. We'll go with that. We
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don't remember this 3.14159 every time,
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right? So that's why I prefer this one.
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All right, let's get input input from
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the user. So all you have to do is
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create a variable radius
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Enter the radius of the circle.
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But remember this gives a string right
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like a string five. We can't do math
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with string. So let's convert it to
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number. So I'm using float.
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Mhm. And now we are ready for math.
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So once we have the radius in pi, the
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formula is super simple. You have to do
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area equal to math dopi
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or you can just give pi
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Right? We don't have r because we wrote
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it as radius that is fine. So pi into
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radius into radius or you can also do
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into two. So this is same as this one no
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change but here we are using the power
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operator. I I hope you have completed
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the operators video and you're here. I
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think you know what this exponentiation
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is all about. So both of them works but
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let's use this one and let's show the
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result using a nice print statement. So
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all you have to do is print
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This is the basic version
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but let's try the better version with
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formatting which is f strings.
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So f the area of the circle is
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or you can write the area of the circle
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and we need this in two decimals.
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and that's it. This makes sure your
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result is rounded to two decimals and
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So now let's try running this one.
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Like for example, enter the radius maybe
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4 cm. The area of the circle with four
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radius is 50.27 which is into r²
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All right, here is the complete program.
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All right, here is the complete program
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which is nice and clean, right? Like you
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just have to import math and you can
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just give radius equal to if you want
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you can also ignore this one.
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Just do this and you can directly give
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math py pi. That also will work
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something like this. And then you can
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just print. Let me remove these
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additional lines so it'll be easy for
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see. So this is how you'll optimize the
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code. You can either create a variable
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and just add math.pi in that in that or
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you can directly use that here.
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So try it out. You can try again. I'll
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show you once again. If you enter the
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radius five like for example.
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So the area of the circle with the
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which is simple and done.
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So let's recap what we have learned. So
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here we worked with input. It is used to
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take the values from the user. And
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always always convert input to float
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when dealing with decimals and use
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when you're working with pi and when you
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deal with more accurate calculations.
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And always format the result with 2F to
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get the clean output especially when
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you're dealing with when you need output
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with two decimals. So if you don't want
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to import the whole math module, you can
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also do this. You can just give this
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and here you can just
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uh do something like from math
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import you can just import pi you don't
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need you know whole math for that and uh
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and then pi will directly deal with this
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so and that's it so this is exercise
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three and we have officially written in
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a program that calculates the area of a
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circle like a pro. If you have enjoyed
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this, hit the like button, subscribe,
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and tap the notification bell. And we
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have got a ton more fun and, you know,
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practical Python exercises coming your
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way. Next up, we'll take this one step
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further with a little twist. So, don't
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miss it and thanks for learning with me
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and I'll see you in the next one.
