Compared to XMLHttpRequest and the libraries built around it, like JQuery.ajax , the fetch API defines a more modern and cleaner way of performing asynchronous requests, based on the use of promises . In this article we will see some of the interfaces provided by the API, like Request and Response , and we will learn how to use the fetch method to perform various types of asynchronous requests. In this tutorial you will learn: How to send asynchronous requests using the fetch method How to...

In a previous article we talked about the various type of JOIN we can use in a MariaDB/MySQL database. This time, instead, we take a look at the UNION statement: how it works, how we can use it to combine the result of queries run on different tables, and what are its peculiarities. In this tutorial you will learn: How to use the UNION statement in a MariaDB/MySQL server What are the properties of the UNION statement The result of an UNION statement

In this series of article about python and HTTP protocol, we work with HTTP requests and responses. In the first article we explore standard library functions such as urllib.request.urlopen or urllib.request.urlretrieve . In the second part we focus on the external "requests" library, which let us perform complex operations, writing less code. HTTP Requests: The standard and the requests library Table of Content PART I The standard library PART II The "requests" library

In the previous article we saw how to perform basic HTTP requests using the python3 standard library. When requests become more complex, or we just want to use less code, and we don't mind adding a dependency to our project, it's possible (and sometimes even recommended) to use the external requests module. The library, which adopted the "HTTP for Humans" motto, will be the focus of this article. In this tutorial you will learn: How to perform HTTP requests with python3 and the 'requests'...

HTTP is the protocol used by the World Wide Web, that's why being able to interact with it programmatically is essential: scraping a web page , communicating with a service APIs, or even simply downloading a file, are all tasks based on this interaction. Python makes such operations very easy: some useful functions are already provided in the standard library, and for more complex tasks it's possible (and even recommended) to use the external requests module. In this first article of the...

In this series of article about Ebay APIs and their use via python and the Ebay python SDK, we see how to setup our working environment and work with the Finding, Trading and Merchandising APIs. Introduction to eBay APIs with python Ebay is one of the biggest e-commerce sites, used by millions of people to buy or sell items worldwide. The Ebay APIs make us able to programmatically perform a lot of operations like managing our online store, finding and comparing prices and more. In this series...

The Ebay Merchandising API is the focus of this fourth and last article of the series dedicated to python and Ebay APIs. This API provides less calls than the ones we previously saw, but among them, one that can be very useful: getMostWatchedItems : we will focus on it. In this tutorial you will learn: What are the calls provided by the Merchandising API How to use the getMostWatchedItems call Introduction to Ebay API with python: The Merchandising API - Part 4

This is the third article of the series dedicated to Ebay APIs and their use via python. In the first article we saw how to setup our working environment , creating a developer and a sandbox "test" account, generating our API keys and installing the python SDK. In the second article we approached the Finding API , focusing on the findItemsByKeywords call. In this article we will introduce the Trading API . In this tutorial you will learn: What are some of the most useful "Trading API" calls...

In the previous article we saw how to perform the preliminary steps to prepare our working environment, create an Ebay developer and a sandbox account and generate the keys and credentials needed to execute API calls. In this new chapter we will create our first request and perform our first call focusing on the "Finding API" In this tutorial you will learn: What are the possible "Finding API" calls; What are the parameters you can use to customize you call; How to build a request with the...

Ebay is one of the biggest ecommerce sites. Many people use it to search and buy products, and many stores use it to enlarge their audience and expand their business range. If we want to operate programmatically on Ebay, for example to mass create or modify a set of items, or quickly confront prices, we must use the dedicated application programming interfaces. In this tutorial we will see how to prepare our working environment in order to use python to interact with the Ebay APIs. In this...

By definition, an higher order function is a function which, at least, receives one or more other functions as arguments or returns another function as its result. In this tutorial we will focus on standard library functions as filter, map and reduce: we will see when they can be useful and how to use them. In this tutorial you will learn: What is an higher order function. Why we can use higher order functions in Javascript. How and when to use filter, map and reduce functions.

The arrow functions syntax was introduced with ECMAScript6: by using this new syntax, in some (but not all) cases, we can produce more concise and readable code, especially when our function contains only one expression. In this tutorial we will see how we can define an arrow function, what are the differences with standard functions and what are the cases in which the use of arrow functions is not appropriate. In this tutorial you will learn: What is an arrow function. How an arrow function...

While previously available via third party libraries, promises were introduced in Javascript, as a native feature, with ECMAScript6. They provide an alternative to callbacks when dealing with asynchronous code, providing, among the other things, a cleaner way to handle errors. In this tutorial we will see how promises work, how to create them and how to use their methods. In this tutorial you will learn: What is a Javascript promise. How to create a Javascript promise. How promises can be used...

The manipulation of files is an operation which sooner or later we'll need to perform in our programs. The python built-in open function returns a file object , which lets us interact with files in different modes: we will see them in this article. In this python tutorial you will learn: How to use the python open function. What are the various modes of operation which can be used with the python open function. How to interact with a file object. Why is important to close a file object, and...

Objective After following this tutorial you should be able to understand how bash arrays work and how to perform the basic operations on them. Requirements No special system privileges are required to follow this tutorial Difficulty EASY Introduction Bash , the Bourne Again Shell , it's the default shell on practically all major linux distributions: it is really powerful and can be also considered as a programming language, although not as sophisticated or feature-reach as python or other...

There are several ways on how to check what version of Java is installed on your system. Most likely the simplest way is to directly use the java binary in combination with the -version option. To do so run java -version on your terminal. $ java -version Check Java Version Furthermore, execute the following command to check the version of the current default Java compiler javac : $ javac -version In case you are looking for a system agnostic way on how to check the Java version installed on...

Objective The objective is to write, compile and execute a basic Hello World java example program. Requirements The only requirement is installed java on your Linux system . Difficulty EASY Conventions

Objective The object of this tutorial is to learn how to modify bash behavior when expanding unset or empty variables using dedicated syntax. Requirements No special system privileges are required to follow this tutorial Difficulty EASY Introduction Variables expansion is one of the most common feature used in the shell: when a variable exists and is part of a command, it is "expanded", so that is substituted by its value. The expansion of empty variables, is one of those things, that if not...

Objective Learning how to extract information out of an html page using python and the Beautiful Soup library. Requirements Understanding of the basics of python and object oriented programming Difficulty EASY Conventions # - requires given linux command to be executed with root privileges either directly as a root user or by use of sudo command $ - given linux command to be executed as a regular non-privileged user Introduction Web scraping is a technique which consist in the extraction of...

Objective Our objective is to create a copy of a PostgreSQL database that is constantly synchronizing with the original one and accepts read-only queries. Operating System and Software Versions Operating system: Red Hat Enterprise Linux 7.5 Software: PostgreSQL server 9.2 Requirements Privileged access to both master and slave systems Difficulty MEDIUM Conventions # - requires given linux commands to be executed with root privileges either directly as a root user or by use of sudo command $ -...