Gabriel Kaszewski
8a921b0423
- Created "My 2023 Coding Edition" post detailing projects and experiences in Rust and game development. - Added "My 2024 and 2025 roadmap" outlining goals and projects for the upcoming years. - Introduced "Python Tutorial - Introduction" and "Python - Variables" posts to teach Python programming basics. - Published "ROADMAP for 2023" to outline initial goals for the year. - Added "My Rust little adventure" post summarizing various Rust projects undertaken. - Released "Spanish Inquisition - 3.0.1 UPDATE" detailing the latest game update and features. - Added multiple background images in AVIF format for website use. - Removed unused SVG files to clean up the public directory.
103 lines
4.7 KiB
Plaintext
103 lines
4.7 KiB
Plaintext
---
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title: "Python - Variables"
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description: ""
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date: "2021-04-25"
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---
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# Variables
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## Set up
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As I mentioned in the previous tutorial, we have to put our text that we want to print out in double-quotes otherwise, Python won't know what we mean.
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In any programming language, there is something called a variable. A variable is something that holds some data.
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## Writing code
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For example, let's define a variable that will store a number of our fingers.
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```python
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fingers = 20
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```
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Now we have defined a new variable which we've called fingers and it stores number 20.
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So in other words this is a variable of Integer type because it stores a number.
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There are a lot of different types that a variable can store.
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| Type | Data |
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| ------- | --------------------------------------------------------------------------------------------------------------------------- |
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| int | Integer numbers e.g 1, 2, 3, 10, 200 |
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| float | Real numbers e.g 1.5, 0.49, 3.14 |
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| complex | Complex numbers |
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| str | Text type e.g 'Hello', "Gabriel", "I love programming" |
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| bool | Boolean type (in other words) True or False e.g True, False |
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| dict | Dictionary type, can store key and its value e.g `fruits_price = {'Orange': 100, 'Apple' : 50}` |
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| list | With this type we can store multiple elements of the same type e.g names=['Anna', 'Sofie', 'Mike', 'Kate', 'Pedro', 'Juan'] |
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We can also modify the values of variables. For example,
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let's write a program that will ask the user how are they.
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Create a file and rename it to _greetings.py_
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```python
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answer = ''
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print('Hello, how are you?)
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answer = input()
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print('Good to hear that you are' + answer)
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```
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As you can see, we can assign value to a variable whenever we want.
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Also, we can concatenate two texts with each other.
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If we had two numbers, we could easily add, subtract, divide, and multiply them.
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Let's write a simple calculator then. Actually it is going to be an adder because of simplicity.
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Create a file and rename it to _adder.py_
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```python
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firstNumber, secondNumber, output = 0,0,0
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print('Welcome to Adder!\nYour first number:')
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firstNumber = input()
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print('Second number:')
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secondNumber = input()
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output = firstNumber + secondNumber
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print('The answer is: ', output)
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```
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## Running code
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To run the first snippet run `python greetings.py`, for the second run `python adder.py`
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## Explanation
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It is time for an explanation. First of all, what does **input()** do?
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The answer is that the **input()** command reads what user types or sends into the standard input device.
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Because of it we can read and interpret data from outside.
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What is **string concatenation**?
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Concatenation is basically adding things with each other and **string concatenation** is adding multiple strings into one.
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Why we can add something like that `print('Good to hear that you are' + answer)` but this `print('The answer is: ', output)` we do in a different way?
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This is a great question!
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As I said before python has types and it uses them to recognize what is what.
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Okay, firstly I encourage you to try and experiment with those snippets and see the outcome yourself.
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But if you are not interested in that, I'll tell you what would happen.
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If we changed this line `print('Good to hear that you are' + answer)` into `print('Good to hear that you are', answer)`,
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nothing would change. But if we changed `print('The answer is: ', output)` into `print('The answer is: ' + output)`,
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the program would display something completely different.
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For example if the first number was 11 and the second was 20 then
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the displayed message would display **The answer is: 1120**. Interesting, huh?
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But why is that?
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As you can see **1120** is the same as **'11'**+**'20'** and not **11** + **20**.
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Because we add to the string **'The answer is: '** a number,
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what python actually does is that it converts **output** into a string and concatenate it.
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But when we pass **output** after the comma, Python doesn't convert it into a string,
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it just passes the data and **print()** displays that.
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In the first scenario `print('Good to hear that you are', answer)` nothing changes
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because **answer** is also a string so concatenation works the way we expect it.
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## Homework
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No homework for today 😊
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