Visit all array combinations with a recursive function

A = [1, 2, 3]
B = [4, 5]
C = [6, 7, 8]

# Visit all combinations of A, B and C values
all = [A, B, C]

# General pointer. Points to the current variable: 0 -> A, 1 -> B, ...
gp = 0
# Internal pointer. Points to the item on the current variable
# Example: gp = 1 --> B selected. ip = 2 --> B[2] selected --> B[2] = 5
ip = [0] * len(all)

def iterator(a):
    # For Python to get gp from global scope
    global gp
    # Weird way in Python to create a for loop. Equivalent in C to:
    # for(int i = 0; i < len(a[0]); i++)
    for i in range(0, len(a[0])):
        # Store current internal pointer
        ip[gp] = i
        # If a has more variables (e.g. a = [[1,2,3], [4,5], [6,7,8]])
        if len(a) > 1:
            # Create subset for the remaining variables, i.e. [[4,5], [6,7,8]]
            # Pythonic way to create an array subset from a given index until
            # end of the array
            b = a[1:]
            # Increase global index as we are about to sweep next variables
            gp = gp + 1
            # Iterate the rest of variables, i.e. [[4,5], [6,7,8]]
            # We came back from lower variables (B and C), so restoring global 
            # pointer to point again to A
            gp = gp - 1
            # Just for result visualization purposes
            str = "["
            # External index and internal index
            for i_ext, i_in in enumerate(ip):
                str = str + "{}, ".format(all[i_ext][i_in])
            # Remove last ", " and add closing ] (cosmetic)
            str = str.strip(", ") + "]"
            print("Indexes = {} --> Values: {}".format(ip, str))

            # ip contains the indexes to all internal variables. Example:
            # Iterating at A[3], B[2], C[1] --> ig = [3, 2, 1] 

Audio Programación

Romancero bot: converting article text into voice with Amazon Polly and sending it to Telegram

The following Python script extracts the content of an article using Readibility (ported to Python), converts it to voice using the Amazon Polly service and finally sends the audio as a voice note to a given user in Telegram using Telethon (Telegram client for Python).

For running the script you will need to install the following Python packages:

pip install boto3
pip install awscli
pip install readability-lxml
pip install telethon

Also, you will need to create a AWS account. If you already have an AWS account, make sure that you have a user created in the IAM Management Console with the following permissions:

User permissions for creating Polly jobs and accessing/writing files in a S3 bucket.

When creating this user, make sure you write down its ID access key and its secret access key. You will need them to configure the aws-cli client.

With this Amazon credentials, you can configure the AWS client by executing the following command:

aws configure

In this step, you will need to fulfill the details with the user credentials you wrote down when creating it.

Now, you will need to create a Telegram API ID. For this, you can go to the Telegram section «Create an Application«. After following the steps described in the official documentation, you will obtain an API ID (it’s a number) and a API hash (it’s a string).

With these steps already completed, you can place all the needed details in the script and run it.

import boto3
import textwrap
import requests
import re
from readability import Document
from telethon import TelegramClient, events, sync
import time
import os

# Configuration

##### Article #####
# Define URL

##### Telegram #####
# Telegram API credentials
api_hash = 'PLACE_API_HASH_HERE'
# Telegram user to send messages
telegram_user = "PLACE_TELEGRAM_USER_HERE"
# Create Telegram client
telegram_client = TelegramClient('session_name', api_id, api_hash)

##### AWS configuration #####
# Get S3 session
session = boto3.Session(profile_name='default')
# Get polly client
polly = session.client('polly')
# Create a S3 client to retrieve the file content
s3 = session.client('s3')
# Define bucket name
bucket_name = 'PLACE_BUCKET_NAME_HERE'
# Get HTML from the article

# Get HTML
response = requests.get(url)

# Extract content with Readibility
doc = Document(response.text)

# Get article body
html_text = doc.summary()

# Regular expression to identify HTML tags, e.g.:
html_tag_re = r"<\\?[^>]+>"

# Remove HTML tags from the article body
text_only = re.sub( html_tag_re, "", html_text,)

# Send message to user pointing to the URL that is going to be converted
telegram_client.send_message(telegram_user, "Converting: %s" % url)

# Convert text to voice

# Start Polly task to save in a Bucket
resp = polly.start_speech_synthesis_task(OutputFormat='mp3',

# Get Polly task
task = polly.get_speech_synthesis_task(TaskId=resp['SynthesisTask']['TaskId'])

# Monitor task status until it is completed
while task['SynthesisTask']['TaskStatus'] != 'completed':
# Wait 2 seconds between server poll
# Get Polly task
task = polly.get_speech_synthesis_task(TaskId=task['SynthesisTask']['TaskId'])
# Print the status of the task
print("Task status: %s" % task['SynthesisTask']['TaskStatus'])

print("Task completed!")

# Retrieve file and send to Telegram user

# Regular expression to extract the key (file name) of the synthesized file
key_re = r'/([0-9A-Za-z-.]+)$'
# Search the regular expression in the OutputUri
regex_search =, task['SynthesisTask']['OutputUri'])
# Take only the first group of the re (key)
file_key =

# Get file name to store in local
title_sanitized = doc.short_title().replace('"', '')
title_sanitized = title_sanitized.replace(':', '')
file_name = "%s.mp3" % title_sanitized

# Download file from the bucket and store it in a MP3 local file
with open(file_name, 'wb') as data:
s3.download_fileobj(bucket_name, file_key, data)

# Delete remote bucket file
# Delete local file
if os.path.isfile(file_key):

# Send MP3 file as a voice note to the telegram user
telegram_client.send_file(telegram_user, file_name, voice_note=True)
# Send signature
telegram_client.send_message(telegram_user, "Message sent from Romancero bot.")

The user you specified will receive a message like this:


Parser in PHP using regular expressions

You can use regular expressions in PHP with the function preg_match ( string $pattern , string $subject [, array &$matches [, int $flags = 0 [, int $offset = 0 ]]] ) . Only the first two paremeters are mandatory and they are the regex and the string where you want to search respectively.

In case of finding a result, preg_match() returns an array where the item at index 0 is the whole match. From 1 onwards they are placed the different groups of your regular expressions (in case there is any). If no match is found, preg_match() returns null.

One of the details that must be taken into account when using regular expressions on PHP is that they must be enclosed by forward slashes (/), e.g. $multiline_meaning_re = ‘/^([A-za-z ,»().\’;:]+)/’; . This regular expression matches any string with any set of letters, spaces, commas, double and single quotes, parenthesis points, colon and/or semicolon.

As a complete example, the following snippet opens a file, parses it to look for English idioms and uploads all of them a MySQL database.

$servername = "";
$database = "";
$username = "";
$password = "";
$conn = mysqli_connect($servername, $username, $password, $database);

// Check connection
if (!$conn) {
    die("Connection failed: " . mysqli_connect_error());

    class Idiom {
        var $idiom = "";
        var $meaning = "";
        var $example = [];
        function print(){
            echo($this->idiom . "<br>" . $this->meaning . "<ul>");
            if(count($this->example) == 0 )
              echo("ERROR!!!!. There should be at least one example");
            foreach ($this->example as $value) {
                echo("<li>" . $value . "</li>");
        function upload($conn){
          $example = "<ul class='list-group'>";
          foreach ($this->example as $value) {
            if($value !== '')
              $example = $example . "<li class='list-group-item'>" . $value . '</li>';
          $example = $example . "</ul>";

          $idiom = mysqli_real_escape_string($conn, $this->idiom);
          $meaning = mysqli_real_escape_string($conn, $this->meaning);
          $example = mysqli_real_escape_string($conn, $example);

          $query = 'INSERT INTO idioms (`idiom`, `meaning`, `example`) VALUES ("'. $idiom . '","'. $meaning . '","'. $example . '")';
          mysqli_query($conn, $query);

    $file = fopen("idioms.txt", "r") or die("Unable to open file!");
    $idiom_meaning_re     = '/^([A-za-z,. -\/()\']+):([A-za-z ,"().\';:\n]+)/';
    $multiline_meaning_re = '/^([A-za-z ,"().\';:]+)/';
    $example_re           = '/^\|--([A-Za-z0-9 \',?.-;$\n"]+[^:])/';
    $new_idiom = 0;
    $new_example = 0;
    $idiom = null;
    $example = "";
    // Output one line until end-of-file
    while(!feof($file)) {
      $line = fgets($file);
      //echo($line . "<br>");
      preg_match($idiom_meaning_re, $line, $matches);

      if($matches != null){
        if($new_example === 1){
          array_push($idiom->example, $example);
          $new_example = 0;
        if($idiom != null){
        $idiom = new Idiom;
        $idiom->example = [];
        $example = "";
        $new_idiom = 1;
        $idiom->idiom = trim($matches[1]);
        $idiom->meaning = trim($matches[2]);
        preg_match($example_re, $line, $matches);
        if($matches != null){
           if($example !== "")
              array_push($idiom->example, $example);
           $new_idiom = 0;
           $new_example = 1;
           $example = trim($matches[1]);
          preg_match($multiline_meaning_re, $line, $matches);
          if($matches != null && $new_idiom){
            $idiom->meaning = $idiom->meaning . ' ' . trim($matches[1]);
          } elseif ($matches != null && $new_example) {
            $example = $example . ' ' . trim($matches[1]);
          } else {
            $new_idiom   = 0;
            $new_example = 0;
    echo("Closing file");



You can find further information about the preg_match() in the PHP official documentation.


Introduction to D3 (Data-Driven Document)

One of the first questions you may ask yourself when getting introduced in D3 is: why are we using selectAll(‘html-tag-name’) method if there is no item to select of that type?

First, let’s see an example of the situation we are talking about:

    const dataset = [12, 31, 22, 17, 25, 18, 29, 14, 9];
    // Add your code below this line'body')
      .text('New Title')
    // Add your code above this line

In the previous example, the only existing HTML tag is <body> . We select body (‘body’) ) and then we perform the .selectAll(‘h2’) . On its own, it makes no sense as the method won’t return any value since no <h2>  tag exists. Nevertheless, it will make sense if we keep looking at the following code.

After the select .selectAll(‘h2’)  we attach the existing dataset to the selected items (.data(dataset) ). Then, we use the enter()  method, which gives meaning to the previous .selectAll(‘h2’) . When using enter() , D3 looks for the number of selected items to bind them with the data. In case of having not enough items in the selection, the enter()  method will create them.

Therefore, as .selectAll(‘h2’)  was empty and the dataset  variable contains 9 elements, it will iterate the code 9 times. In case of having already created some  <h2>  elements, it will simply fulfill the HTML code the necessary iteration to cover all the dataset  elements. Remember that who does this iteration is  the data() method.  It parses the data set, and any method that’s chained after data() is run once for each item in the data set.

You can find more information in the official documentation at the website.


In D3 there exists the Scale function to change the value of the data set so that it can fit in the screen. Two important methods are range() and domain(). The domain method covers the set of input values whereas the range function convers the set of output values. Let’s see an example:

const scale = d3.scaleLinear();
scale.domain([50, 480]);
scale.range([10, 500]);

scale(50) // Returns 10
scale(480) // Returns 500
scale(325) // Returns 323.37
scale(750) // Returns 807.67

From freeCodeCamp:

The domain()  method passes information to the scale about the raw data values for the plot. The range()  method gives it information about the actual space on the web page for the visualization.


Web scraper with Scrapy

#!/usr/bin/env python
# -*- coding: utf-8 -*-

import scrapy
import re

title_regex       = r'Letra de\s+([a-zA-Z0-9áéíóúñü_,!¡¿?"() ]+)\s-'
empty_lines_regex = r"^\s+$"
tabs_regex        = r"^[\n\t]+"

class ConchaPiquerSpider(scrapy.Spider):
    name = 'conchitabot'
    allowed_domain = ['']
    start_urls = ['']
    custom_settings = {
        'FEED_EXPORT_ENCODING': 'utf-8',
    BASE_URL = ''
    def parse(self, response):
        lyric_links = response.css(".lista_uno li a::attr(href)").extract()
        for link in lyric_links:
            absolute_url = self.BASE_URL + link
            yield scrapy.Request(absolute_url, callback=self.parse_lyric)
        lyric_names_raw = response.css(".lista_uno li a::text").extract()

    def parse_lyric(self,response):
        raw_titles = response.css("h1").extract()
        for raw_title in raw_titles:
            match =, raw_title.encode("utf-8"))
            if match:
                title =
        raw_text = response.css("#HOTWordsTxt::text").extract()
        encoded_text = []
        single_string = ""
        for item_text in raw_text:
            single_string = single_string + item_text

        lyric = self.clean_lyric(single_string)

        text_file = open("./letras/" + title + ".txt", "w")

    def clean_lyric(self,dirty_str):
        encoded = dirty_str.encode("utf-8")
        no_spaces = re.sub(r"^\s+", '', encoded)
        no_tabs = re.sub(r"[\n\t]+", '', no_spaces)
        return no_tabs
#!/usr/bin/env python
# -*- coding: utf-8 -*-

import os
import re

def get_sorted_files(Directory):
    filenamelist = []
    for root, dirs, files in os.walk(Directory):
        for name in files:
            fullname = os.path.join(root, name)
    return sorted(filenamelist)

text = "<head><meta charset='utf-8'>"
folder = "./letras/"
files = get_sorted_files(folder)
for filename in files:
    filebase = re.sub(folder, "", filename)
    filebase = re.sub("\..*$", "", filebase)
    with open(filename,'r') as f:
        text = text + "<h1>" + filebase + "</h1><pre>" + + "</pre>"

unified = open("unified.html", "w")