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Friends in this video

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we are going to see how to provide input for your Python

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Script while running, and how to provide output from your

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Python Script,

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and also we are going to see the usage of 'eval' function.

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Right. So guys, here I'm explaining this concept from my Linux

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box. I'm opening my Linux terminal, right. From there

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I am going to explain about this.

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And you can also try the same thing, whatever

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I am trying from Unix, or Unix-like systems, or Linux, even

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on your Windows as well without any change. The only thing

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on our Windows we configured Python as simply 'python', but

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here Python is like 'python 3' name, right. Fine.

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Let me write simply a script called 'input_output' script,

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'.py'. So guys,

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I am going to design a simple calculator, arithmetic calculator,

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so "simple arithmetic calculator".

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So I am fixing numbers like 'a=', and 'b=', right,

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then I am finding the 'result=a+b', and I am

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trying to print.

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[no audio]

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"The addition of and is". So here

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I am trying to print my 'result'.

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[no audio]

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Fine. So this is our script, whatever we have. Now

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I am going to print the 'result' with the help of Python 3, not with,

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so if you see simply 'python', then it will work from Python 2.

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In Python 2 you don't have like this syntax "f", formatted

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string you don't have. Only in Python 3 it is there. So

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'python3 input_output'. It's working perfectly.

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But if you observe our script is like "simple arithmetic calculator",

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or simply addition. Let me give only option as addition,

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"simple addition calculator" because I'm not doing here as

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of now addition, subtraction, multiplication, division,

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let me do the only simply addition.

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[no audio]

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Right. So whatever the script you have as of now that script if

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you run with any number of times your output would be always

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12, for 4 and 8.

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Right. But my requirement is, if it is an addition calculator

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while running in this way, our script has to ask "Enter your

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so-and-so number", "Enter your b number", and then it has to

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give the 'result'. Each time

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it has to ask. Each time

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it has to take two numbers, then it has to find the 'result'.

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But as of now we are fixing our values 'a' and 'b' inside

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of your script, but I don't want to do in that. Then what I

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can do is, instead of 'a=4' always,

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I am going to read my number from command line.

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So for that this is the syntax. "Enter a value".

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So whatever you're writing inside of your input parenthesis

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in terms of quotations, that will be printed as it is

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on your command line. Then let me take even for 'b' also input,

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"Enter b value".

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[no audio]

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Right. So as of now, I am not going to perform your 'result' because

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I want to show you something. 'print(

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'The value of a is: )', and 'type is', I mean, what is

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the data type, I want to print that. So 'type(a)'.

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[no audio]

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Right. Okay, let me check it.

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You can check even for 'b' also. I am taking only for 'python',

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sorry spelling mistake, 'python'.

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Something wrong.

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Where is it?

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[no audio]

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'type(a)', 'print', okay.

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Sorry, we are using 'python'.

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It's not 'python', 'python3' because we are working with Python 3

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version. Only in Python 3 version

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we have 'f', formatted strings.

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Okay, see that?

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Yeah, before that let me show you your script once. So this is your script.

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You know, whenever if you run your Python Script it will

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run from top to down, and while running if any line starts

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with a '#' symbol that line won't execute, simply it will skip.

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Now you have only three lines in your program, these two and this line.

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So because of 'a=input', first your script will take

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'input' with this command some value from command line.

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Let me enter some value 45 and some 'b' value, then see the

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output. You are getting value 45 like a string but you know

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that is a number. We want to feel that as a number but your

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Python 3 is taking with the help of 'input', right, that as a

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string. So whatever the 'input' you are providing that is always

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a string if you read that with the help of 'input'.

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Right. But whereas in Python 2 you have 'input' to read numbers

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and you have 'raw input' to read strings but here there is a common,

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common input is there, common input statement is there that

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is 'input' through which whatever you are reading from command

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line that is always a string. Then how you can convert to your

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required data type?

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We have different things,

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I mean different types.

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Let me open my Python 3 terminal. Guys, whatever we are going

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to discuss now that will work only with Python 3 not with Python 2.

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Let's say 'x= input', right, "enter x:".

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[no audio]

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So I'm entering something. What happened?

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Yeah, I have started with single quotation and ended with double

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quotation. That's wrong.

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[no audio]

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'Enter x: ', I am entering something called 56.

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[no audio]

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Right. Then, see that. 'type(x)' is string but I want to feel that

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as a number integer.

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So that's why while reading, you know type conversion we

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have, right. So simply

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[no audio]

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you can write in this way.

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[no audio]

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Read and then convert into as a integer. This is one way.

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[no audio]

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So whatever you are entering from your command line, something wrong.

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[no audio]

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Indentation. Yeah, no problem.

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[no audio]

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Read something and convert that into integer. Now see that,

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'print(type(x))',

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[no audio]

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integer, right. Or else you have one more default function

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called 'evaluation'. Using this based on whatever the data you

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are entering your Python will identify

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what type of data you are entering.

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Let me enter some 3.4, right. Now 'print(type(x))',

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[no audio]

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float. So 'evaluation' function will automatically convert your given

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data into particular data type.

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Anyway, 'input' is only to read strings.

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But if you want to read some other values you have to use

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evaluation, right.

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Fine. Let me do one thing.

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I am going to repeat same.

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[no audio]

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'input("Enter x")'. Now I am going to enter a string called

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"hi", right. See, 'hi' is not defined. It is not taking. So whenever

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if you are using evaluation and whenever if you are providing

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string. Anyway by default input is read

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read to string. But whenever if you're using evaluation

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[no audio]

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you have to provide your string as a quotations. That's it.

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Now 'print(type(x))'.

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[no audio]

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That's it.

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Okay. So be clear. Use 'x=eval(input("Enter"' your required

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thing, and whenever if you are entering string please provide

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in terms of quotations.

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Otherwise, if you want to read only strings simply use this

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one, enter your string.

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[no audio]

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And in this case, you don't need to provide anything inside

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of your quotation. Simply you can write.

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Hi, Hello, that's it, right. Now see 'print(x)'. It will work.

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So whenever if you use evaluation function for your 'input',

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then you have to write your quotation inside of double quotes.

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Right. Okay. Now, let me design your simple calculator.

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[no audio]

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so 'input'

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[no audio]

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'evaluation'

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Okay. This is the syntax to read your numbers.

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Of course, you can also use type conversion but I am using

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this one. This is of course somewhat better, right?

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So I will show you that as well guys.

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[no audio]

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So first of all observe your script. You're having now this many

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number of lines, 1, 2, 3, 4, 5, because of first line if I run

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my Python Script with python3, right, because of first line

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it is reading something, second line

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it is reading something, then you are getting 'addition', 8, and

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type is integer for your 'a'. Even 'b' is also same, right. So same program

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you can also write in this way without any confusion.

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Let me comment first all these lines.

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[no audio]

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So what I am doing is 'a=int', but this syntax

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will work only to read integer numbers, but you may enter

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integer or, right, some float or maybe some complex sometimes,

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so that's why I don't prefer this one.

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[no audio]

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Right. So I don't prefer this actually, but just there is

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one more option in case if you want to work purely with

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integers, right. Then at that time you can take this one.

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[no audio]

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But by using evaluation automatically it will identify whatever

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the data you are entering, right?

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[no audio]

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So I'm entering 4, 5, see that 9, integer, but if I

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enter something like

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5.7,

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right,

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[no audio]

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it is not accepting because

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it need only integer values.

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Right. But if I use simply with evaluation it will work

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perfectly. So that's the reason if you want to read anything

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from command line just try to use evaluation of your input

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and at that time in case if you want to provide any strings,

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you have to write your strings in terms of quotations.

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But anyway, as of now, we are going to work with numbers

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only. Let me take 4.5 and 9.,

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some 2 see the result.

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It's working perfectly.

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So that's why guys this is my suggestion, try to use because

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while going forward anyway, definitely all organizations will use

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Python 3 only that's why just try to remember in this way

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to read inputs. Okay.

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Okay guys, thank you for watching this video.

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[no audio]