<center>![p1.png](https://steemitimages.com/DQmU3VQGGHcbE5JyZBGTF8iN1d1xustawjxytWr4bP5kMNt/p1.png)</center>
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In the past episode we learned the absolute basics how to execute the script and how to print out (display) text in the terminal:
* https://steemit.com/programming/@profitgenerator/learn-basic-python-programming-ep-1

In this episode we are going to learn how to use variables and how to interact wit the script, by inputting things from the keyboard.

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# Variables

In python you don't need to declare variables (str,int,float,double) like in C++, the code itself automatically detects what kind of variable it is, so it's very easy to use for novices. Essentially you can transform or specify later on, but not always needed.

Let's go back to our `test.py` file, and see how to use variables. Well basically you just write the variable name, an `=` and the value of the variable. For numbers you just write the number , for a string variable, like a text, you just write it in the string wraps `"` or `'` we learned in the past episode.

![1.png](https://steemitimages.com/DQmVPyXa3zxcUZ3M1inRrd4j5zcjrQXDwU7NM9ob8bBTPsY/1.png)

Which will display:

![2.png](https://steemitimages.com/DQmVvzrZm56vx1NCdeEEgWqzPut2pbsNyG3tyH2iFAD1TMU/2.png)

So we have just substituted the argument of the `print` with a variable, instead of writing `print "text"` we just use the variable `text_variable` to contain the data `"text"` and we print it out this way.

Also note that a number can be a `string` too however if we put the number in the `""` wraps it becomes a string variable, and only string operations can be done with it like concatenation, trimming ,separation into characters and such. While an integer can only be used mathematically, like addition, division ,etc...

It may display the same value, but it's a different kind of variable used for different purposes:

![T2.png](https://steemitimages.com/DQmV2bg7yYxr49Hhz8M3njwjzk47kssMqiNUj3c5P9dAXut/T2.png)

Displaying:

![T1.png](https://steemitimages.com/DQma2zqu99kynEfWVkakPW3qpdyS39drTdLZe8vpaus9wqD/T1.png)


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# Math Operations

Well you just use the basic operators `+ * - / ` just like in any other math software. Then give value to your variables that you want to calculate from, and perform the operation. It would work just fine, obviously you can't divide by 0 and things like that, but otherwise it should work fine.

![M1.png](https://steemitimages.com/DQmdCoiq3eG1W4Pm1AwLSJK1yv7AHs8ucBbnTvELTvpasvg/M1.png)

Displaying:

![M2.png](https://steemitimages.com/DQmexutbV5XuQ1SQYYj4E5nBgzALsVJoXVgQQ9mvzwfAAUs/M2.png)

It works just fine, except for division, it's because all math variables are by default integers I believe, and a division, unless it's a round number, will always give out fractions, which is a [float variable](https://en.wikipedia.org/wiki/Floating-point_arithmetic) with decimal points after it. In python we use the `float()` function to turn the number into a float variable, but then we have to transform each variable into float, or we make the initial variable float by adding a `.0` decimal to the number.

So either like this:


![f1.png](https://steemitimages.com/DQmebk67m9NQiDtWBHrD67YyvUbZDAWsBLWgHRVPVAJKyMo/f1.png)

Or like this:

![f2.png](https://steemitimages.com/DQmec55zJahHrifgQY3s78ELPBqiwnMAVDzPTaRXjcLKy8e/f2.png)

Both displaying the correct values this time:

![f3.png](https://steemitimages.com/DQmNSqpZuFzTirLMRzJALdGmPNqb12NAoVc1MTenzUoJKc4/f3.png)


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# Inputs

Now let's interact with the script, let's input the values of A and B directly from the keyboard from the terminal. For this we are going to use the `raw_input()` function. Every time this is called, the terminal will be waiting for a text input. So you write something in the terminal, and you finalize it by hitting `Enter` on the keyboard. So in this case the `raw_input()`will be called 2 times separately for A and B, which means that you will have to enter a number, then hit enter, and then enter another number. The order is as specified in the script, in our case the first one is A. We also have to transform it into `float()` since the `raw_input()` is a string based function.


![r1.png](https://steemitimages.com/DQmNdjJg5X3jKW99Wnhov6VWoN1R8Xub52SgTWGuLfCcVCc/r1.png)


Of course B can't be 0, we can't divide by 0, and you can't enter a text, otherwise it will be an error. So just enter 2 numbers:

![r2.png](https://steemitimages.com/DQmSq57TX7bwQ8EhdUZbdsvLvJAT41XaPzf5DcqTqJ37PsW/r2.png)

So I have entered 56 for A, hit enter and 14 for B and hit enter. Then it displayed the results of those calculations.

**And hence this is how you created your very first calculator software, it's just this easy!**

### Essentially, let's make it more user friendly and add instructions inside it:

![ca1.png](https://steemitimages.com/DQmSkFy3DxnCPx1TgKWgciYbx7Vo8iLYWz4eEwjPPv7osvw/ca1.png)

Note that we can't combine float variable with string, so we have to turn the float into string with the `str()` function. And adding together 2 strings is called [concatenation](https://en.wikipedia.org/wiki/Concatenation) which is done with `+` operator. It means that the 2nd string will be put after the end of the first one.

![ca2.png](https://steemitimages.com/DQmUsfo8ATB42RK7xAbaSxkfGmZfNQS6optewzVFNFqnN9t/ca2.png)

### So that is how you have your first calculator ready to calculate for you.

Stay tuned for the next episode, I will be teaching you even more interesting stuff about programming!

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**Sources:**
* https://pixabay.com
* Python is a trademark of the [Python Software Foundation](https://www.python.org/psf/)



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