Often we see “invalid data”, “clean data”, “normalize data”. What does it mean as to practical data extraction and how does one deal with that? One shot is better than 1000 words though:
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Author: admin
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Simple text analysis with Python
Finding the most similar sentence(s) to a given sentence in a text in less than 40 lines of code 🙂
Working with a Backconnect proxy service (Oxylab.io) we spent a long time looking for a way to authorize it. Originally we used JSoup to get the web pages’ content. The proxy()Â method can be used there when setting up the connection, yet it only accepts the host and port, no authentication is possible. One of the options that we found, was the following:
Â
function strip_tags(str){
const tags = ['a', 'em', 'div', 'span', 'p', 'i', 'button', 'img' ];
const tagsAndContent = ['picture', 'script', 'noscript', 'source'];
for(tag of tagsAndContent){
let regex = new RegExp( '<' + tag+ '.*?</' + tag + '>', 'gim');
str = str.replace( regex ,"");
}
for(tag of tags){
let regex1 = new RegExp( '<' + tag+ '.*?>', 'gim');
let regex2 = new RegExp( '</' + tag+ '>', 'gim');
str = str.replace(regex1,"").replace(regex2,"");
}
return str;
}
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JavaScript, Regex match groups
Often we want only a certain info from the matched content. So, groups help with that.
The following example shows how to fetch the [duplicate] entry index from the error message. For that we take 1st group, index “1”:
const regex = /Duplicate entry\s'([^']+)+'/gm;
const str = `{ Error: (conn=42434, no: 1062, SQLState: 23000) Duplicate entry '135' for key 'PRIMARY'
sql: INSERT INTO \`test\` (id , string1) values (?,?) - parameters:[[135,'string 756']]
at Object.module.exports.createError (C:\\Users\\User\\Documents\\RnD\\Node.js\\mercateo-`;
let m;
while ((m = regex.exec(str)) !== null) {
// This is necessary to avoid infinite loops with zero-width matches
if (m.index === regex.lastIndex) {
regex.lastIndex++;
}
// The result can be accessed through the `m`-variable.
m.forEach((match, groupIndex) => {
console.log(`Found match, group ${groupIndex}: ${match}`);
});
}As developers scrape data off the web, we use Node.js along with handy Cheerio scraper. When fetching .html() Cheerio parser returns the special symbols as HTML encoded entities, eg.:ä as ä ß as ß
Cheerio developer vindication of the parser action
(1) It’s not the job of a parser to preserve the original document.
(2) .html() returns an HTML representation of the parsed document, which doesn’t have to be equal to the original document.
source.
Imstall mariadb package:
npm i mariadb
The code
const config = require("./config");
const db = config.database;
const mariadb = require('mariadb');
const pool = mariadb.createPool({
host: db.host,
user: db.user,
password: db.password,
database: db.database,
connectionLimit: 5
});
async function asyncSaveDataDB(data) {
let conn;
try {
conn = await pool.getConnection();
const rows = await conn.query("SELECT 1 as val");
console.log(rows); //[ {val: 1}, meta: ... ]
const res = await conn.query("INSERT INTO test (string1) value (?)", [data]);
console.log(res); // { affectedRows: 1, insertId: 1, warningStatus: 0 }
} catch (err) {
throw err;
} finally {
if (conn) return conn.end();
}
}
async function asyncSaveDataBulkDB(arr) {
let conn;
try {
conn = await pool.getConnection();
conn.batch("INSERT INTO `test` (string1) values (?)", arr)
.then(res => {
console.log(res); // 2
});
} catch (err) {
throw err;
} finally {
if (conn) return conn.end();
}
}
if (module.parent) {
module.exports = { asyncSaveDataDB, asyncSaveDataBulkDB }
} else {
asyncSaveDataBulkDB(['tt6', 'test 8']);
}Config.js might look like the following:
module.exports = {
database:{
host: "185.221.154.249",
user: "xxxxxxxxx",
password: "xxxxxxxxx",
database: 'xxxxxxxxx'
}
}
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Centos 7, Node.js, MySQL connect
I’ve mariadb installed on my VDS with Centos 7.
I’ve installed mysql npm package:
npm i mysqlYet requesting that package with
var mysql = require('mysql');
has not provided to the successful connection.
While
var mysql = require('mariadb');
has done.
var mysql = require('mariadb');
var con = mysql.createConnection({
host: "localhost",
user: "admin_default",
password: "xxxxxx",
database: 'admin_default'
}).then(function (){
console.log('connected!');
}, function(err){
console.log(err);
});
//console.log(con);
Given: a webpage to scrape.
If you inspect the DOM tree of that page you will find that quite a few tags are having the keyword dist. As an example:
<link rel="shortcut icon" type="image/x-icon" href="/wcsstore/ColesResponsiveStorefrontAssetStore/dist/30e70cfc76bf73d384beffa80ba6cbee/img/favicon.ico"><link rel="stylesheet" href="/wcsstore/ColesResponsiveStorefrontAssetStore/dist/30e70cfc76bf73d384beffa80ba6cbee/css/google/fonts-Source-Sans-Pro.css" type="text/css" media="screen">
Imperva (that includes the former Distil anti-bot management) is a service providing many kinds of website protections. The present Imperva services include the following ones:
- Cloud Web Application Firewall (WAF)
- Bot Protection service (formerly Distil Networks)
- IP Reputation Intelligence
- Content Delivery Network (CDN)
- Attack Analytics solution (eg. DDoS)
As to the protection of the bot scraping activities we mention the following.