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Tag: programming

Python: Getting page title

Published by Silveira on 26 May, 2020 
# Get the HTML page content
from urllib import request
html = request.urlopen("https://silveiraneto.net").read()

# Get the title tag
from bs4 import BeautifulSoup
title = BeautifulSoup(html, 'html.parser').find('title')

print(title.string)

This uses the XML/HTML library BeautifulSoup . This could also be done using regex but playing with HTML and regex is usually a bad idea.

Cedilha no Ubuntu 16.04

Published by Silveira on 5 March, 2017 
    çççç
  ççç  ççç 
  ççç  ççç 
  ççç 
  ççç 
  ççç  ççç 
    çççç
     çç
    çç

Fiz esse script (cedilha.sh) pra fazer o c-cedilha (ç) funcionar no Ubuntu 16.04. Como é uma tarefa chata que eu já tive que fazer muitas vezes fica mais fácil pra mim ter um script pra fazer isso e pode ser que seja útil a outras pessoas. Infelizmente é uma solução que exige baixar e executar como root um script da internet. Eu recomendo que você leia o script e entenda o que está acontecendo antes de executá-lo. Esse script altera vários arquivos importantes e ele faz um backup (.bak) desses arquivos.

wget https://raw.githubusercontent.com/silveira/cedilha.sh/master/cedilha.sh
sudo bash cedilha.sh

Por favor, se o script funcionou pra você também, diga nos comentários. Se você não está usando Ubuntu 16.04 e quer testar o script ainda assim, edite o script e remova a verificação no inicio do programa.

parallel counting in Java using AtomicInteger

Published by Silveira on 30 September, 2015 
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.TimeUnit;

class ParallelCounterExample {
   public static void main(String[] args) throws InterruptedException {
      int threads = 2000;
      ExecutorService executor = Executors.newFixedThreadPool(threads);
      final AtomicInteger atomi = new AtomicInteger();
      for(int i=0; i<threads; i++) {
         executor.execute( new Runnable() {
            @Override
            public void run() {
               atomi.getAndIncrement();
            }
         });
      }
      executor.awaitTermination(1, TimeUnit.SECONDS);
      executor.shutdown();
      System.out.println(atomi.get());
    }
}

Regex with negatives lookahead and lookbehind

Published by Silveira on 22 June, 2015

"Looking different directions" by Paul Kline at (https://www.flickr.com/photos/paulelijah/6717953239/)
“Looking different directions” by Paul Kline.

Problem: Match strings that contains a single quotation mark ('), but not multiple ones together.

Solution:

(?<!')'(?!')

This is a regex for a single quotation mark with a (?<!') in the left and a (?!’) in the right. The (?<!') is a ?< look behind if not ! a single quotation mark '. The (?!') is a look ahead ? if not ! a single quotation mark '.

Java code:

import java.util.regex.Pattern;

public class RegexProblem {
  public static void main(String args[]) {
    Pattern single_quote = Pattern.compile("(?<!')'(?!')");
    String[] phrases = {
      "",
      "'",
      "a'a",
      "aaa",
      "aa'aa",
      "aa''aa",
      "aa'''aaa",
      "aaa''''aaa"
    };
    for(String phrase: phrases){
      System.out.println(String.format("For %s is %s.", phrase,
            single_quote.matcher(phrase).find()));
    }
  }
}

The output is:

For  is false.
For ' is true.
For a'a is true.
For aaa is false.
For aa'aa is true.
For aa''aa is false.
For aa'''aaa is false.
For aaa''''aaa is false.