title: Scrapy web crawler's css & xpath selectors vs BeautifulSoup
body: <p>I'm using Scrapy for a large scale project and a significant part of the computation goes into parsing the web pages.</p>
  
  <p>I was wondering if the <code>css</code> and the <code>xpath</code> selectors of Scrapy are optimized for the best algorithmic efficiency or should i use <code>BeautifulSoup4</code> which happens to use lxml internally.</p>