Free knowledge blog: linux, programming, open source, databases, android, frameworks, web and computing in general

Creating an API REST with Python, Flask and SQLite3

In this Python programming tutorial you will learn how to create a REST API using Flask, SQLite 3 (for data), and JSON for data communication.

In the end you will have an API that you can consume from any client that could be an Android application, a browser with JavaScript or even another server language.

I will show you how to create an API that communicates using JSON and saves the data in SQLite 3. The API will be created with Flask, and we will use the Python programming language to handle all the data.

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By parzibyte, ago

Tetris game in JavaScript – Open source

In this post I will show you the Tetris game programmed in pure JavaScript, totally free and open source.

This block game is programmed with JavaScript and uses canvas to paint the game. I also use Bootstrap for the layout of the buttons and the page in general, with a bit of SweetAlert for the alerts.

Although it seems simple to do, it is one of the jobs that has cost me the most and of which I am most proud. It was complex (for me) to understand all the logic for collisions, rotations, row deletion, part movement, limits, etc.

Among the features of the game we find:

  • Sounds: background music, sound when the piece cannot be rotated, when a complete row is made and when the tetromino touches the ground
  • Colors: each piece has a random color chosen at runtime
  • Rotations: pieces can be rotated to accommodate them and accumulate points
  • Mobile compatible: because it is web, I have added some buttons to be able to play it on mobile phones and tablets, but it can also be played with the keyboard
  • Open source: you can modify the game, the board, the length, speed, pieces, rotations, etc.
  • Tetris port: behaves like any normal tetris game
  • Game pause: the game can be paused or resumed at any time

Let’s see then the details of this game programmed in JS. Throughout the post I will show you how this game is programmed, I will also leave you a demo and the complete code which is FOSS.

Note: figure, piece and tetromino will be used synonymously in this post.

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By parzibyte, ago

API REST with Go and MySQL

In this article about programming in the Go language (also known as Golang) we will see how to create a REST API that communicates through JSON, saving and displaying data from a MySQL / MariaDB database.

In the end we will have a REST API with Go using the 4 methods: POST, PUT, DELETE and GET using the Mux router. We are also going to implement the 4 operations of a database: insert, update, delete and select.

I will leave the full open source code at the end of the post.

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By parzibyte, ago

Enable CORS in Flask app

In this post I will show you how to enable CORS (Cross Origin Resource sharing) so that you can make HTTP requests from a different domain than the one you use for your Flask application written in Python.

We will just add a kind of middleware to modify all the responses and add the headers that allow CORS in Flask.

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By parzibyte, ago

Connect 4 in JavaScript and HTML

In this post I will show you how to program the Connect 4 game by using JavaScript with HTML and Vue, with Bootstrap styles.

Connect 4 in JavaScript, HTML - Web version

Connect 4 in JavaScript, HTML – Web version

It is the Connect 4 game but web version with a player versus player option, as well as player versus CPU that uses a small artificial intelligence.

Throughout the post I will show you how the game works, what technologies I have used, styles, etc. I will also show you how to download the source code, as the game is totally free and open source. Finally I will leave you a demo to play connect 4 online.

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By parzibyte, ago

Java: binary to text translator

In this post about Java I am going to teach you how to convert text to binary, and binary to text. That is, make a type of text – binary translator in Java to be able to convert between both formats.

Another way to call this is to say “Binary to English translator” for example.

Text to binary translator in Java

For example, convert 1110000 1100001 1110010 1111010 1101001 1100010 1111001 1110100 1100101 101110 1101101 1100101 to “parzibyte.me” and vice versa.

All this programmed in Java with manual methods and custom logic.

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By parzibyte, ago
Imprimir códigos QR en impresora térmica

How to print QR codes on Thermal printer

Summary: In this post I will show you how to print readable QR codes on a thermal printer (also called ticket printer, pos printer, etc.) using JavaScript and a plugin.

If you have followed my posts, you will know that a long time ago I developed a plugin and I have added new features, until today we print QR codes on a thermal printer.

Some time ago I showed you how to print a ticket /receipt directly from browser, today we will use it to print a QR code.

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By parzibyte, ago

PHP & MySQL tutorial using PDO

Although there are millions of tutorials about MySQL and PHP, I decided to make mine but in a very very simple way. Before you start, you must have a basic knowledge in MySQL.

MySQL and PHP connection using PDO

Source code of PHP file connection

It is worth mentioning that we will not see good practices of databases, relationships, etc. We will use the tables as they are, without looking at normalization, or things like that.

Note: this tutorial uses PDO, but remember that we can also use mysqli functions. Personally I recommend PDO, because it is object oriented. However, I hope to write a tutorial about mysqli in the future.

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By parzibyte, ago
MySQL and PHP connection using PDO
How does the plugin for thermal printers work

A plugin for printing in thermal printers directly from browser

In this post I will introduce to you a plugin for printing tickets, receipts or invoices on a thermal printer using client-side JavaScript even if your web page or application is on a cloud server.

This plugin allows you to print directly from browsers, without dialogs and without browsers compatibility issues because you only have to send a HTTP request to print silently and in the background.

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By parzibyte, ago

Print receipt in thermal printer using JavaScript, CSS & HTML

In this post I will show you how to print a ticket or receipt by using JavaScript (client side) and a thermal printer. At the end we will have a great ticket that looks like this:

Ticket sample

Receipt printed in thermal printer using JavaScript only

Obviously you can change the font family, size, logo and so on. And remember: we will be using only pure CSS, HTML & JavaScript, no frameworks; though you can use any framework to render the content before printing.

You can see the demo here, and the full code on my GitHub.

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By parzibyte, ago
Ticket sample
Diálogo con layout personalizado en Android

Custom alert dialog in Android

Dialog and AlertDialog with custom layout on Android

In this post I will show you how to create custom dialog on Android using a layout created by us, that is, create a custom alert by adding elements such as EditText, Button, etc.

Custom alerts on Android serve to display an alert that is not a confirmation alert, since we can define a custom layout.

To achieve this we will use the Dialog and AlertDialog.Builder classes.

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By parzibyte, ago

How to redirect in Spring Boot

Redirect in the Spring Boot framework

In this post I will show you how to redirect or direct the user to another URL within the method of a controller in the Spring Boot framework.

Redirecting to another URL in Spring Boot is very useful when the user does a certain action and we must return it to the main page.

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By parzibyte, ago

Change express-generator app port

The express-generator package helps a lot in the development of web applications with Node, because it generates the skeleton of an application.

A small disadvantage is that, when generating the code, we do not know how to change some very basic things, for example, the port on which the app listens (the default port is 3000).

In this post I will show you how to change the port in some app generated by express-generator. (more…)

By parzibyte, ago