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rvestvscrwlr-crawler

MIT 17 1 1,455
629.3 thousand (month) Nov 22 2014 1.0.4(1 year, 7 months ago)
298 2 2 MIT
v1.7.2(17 days ago) Apr 18 2022 12 (month)

rvest is a popular R library for web scraping and parsing HTML and XML documents. It is built on top of the xml2 and httr libraries and provides a simple and consistent API for interacting with web pages.

One of the main advantages of using rvest is its simplicity and ease of use. It provides a number of functions that make it easy to extract information from web pages, even for those who are not familiar with web scraping. The html_nodes and html_node functions allow you to select elements from an HTML document using CSS selectors, similar to how you would select elements in JavaScript.

rvest also provides functions for interacting with forms, including html_form, set_values, and submit_form functions. These functions make it easy to navigate through forms and submit data to the server, which can be useful when scraping sites that require authentication or when interacting with dynamic web pages.

rvest also provides functions for parsing XML documents. It includes xml_nodes and xml_node functions, which also use CSS selectors to select elements from an XML document, as well as xml_attrs and xml_attr functions to extract attributes from elements.

Another advantage of rvest is that it provides a way to handle cookies, so you can keep the session alive while scraping a website, and also you can handle redirections with handle_redirects

This library provides kind of a framework and a lot of ready to use, so-called steps, that you can use as building blocks, to build your own crawlers and scrapers with.

Some features: - Crawler Politeness innocent (respecting robots.txt, throttling,...) - Load URLs using - a (PSR-18) HTTP client (default is of course Guzzle) - or a headless browser (chrome) to get source after Javascript execution - Get absolute links from HTML documents link - Get sitemaps from robots.txt and get all URLs from those sitemaps - Crawl (load) all pages of a website spider - Use cookies (or don't) cookie - Use any HTTP methods (GET, POST,...) and send any headers or body - Iterate over paginated list pages repeat - Extract data from: - HTML and also XML (using CSS selectors or XPath queries) - JSON (using dot notation) - CSV (map columns) - Extract schema.org structured data in JSON-LD format from HTML documents - Keep memory usage low by using PHP Generators muscle - Cache HTTP responses during development, so you don't have to load pages again and again after every code change - Get logs about what your crawler is doing (accepts any PSR-3 LoggerInterface)

Example Use


library("rvest")

# Rvest can use basic HTTP client to download remote HTML:
tree <- read_html("http://webscraping.fyi/lib/r/rvest")
# or read from string:
tree <- read_html('
<div class="products">
  <a href="/product/1">Cat Food</a>
  <a href="/product/2">Dog Food</a>
</div>
')

# to parse HTML trees with rvest we use r pipes (the %>% symbol) and html_element function:
# we can use css selectors:
print(tree %>% html_element(".products>a") %>% html_text())
# "[1] "\nCat Food\nDog Food\n""

# or XPath:
print(tree %>% html_element(xpath="//div[@class='products']/a") %>% html_text())
# "[1] "\nCat Food\nDog Food\n""

# Additionally rvest offers many quality of life functions:
# html_text2 - removes trailing and leading spaces and joins values
print(tree %>% html_element("div") %>% html_text2())
# "[1] "Cat Food Dog Food""

# html_attr - selects element's attribute:
print(tree %>% html_element("div") %>% html_attr('class'))
# "products"
<?php
require_once 'vendor/autoload.php';

use Crwlr\Crawler;

$crawler = new Crawler();
$crawler->get('https://example.com', ['User-Agent' => 'webscraping.fyi']);


// more links can be followed:
$crawler->followLinks();

// and current page can be parsed:
$response = $crawler->response();
$title = $crawler->filter('title')->text();
echo $response->getContent();
```

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