rvestvstyphoeus
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
Typhoeus is a Ruby library that allows you to make parallel HTTP requests, which can greatly speed up the process of making multiple requests to different servers. It is built on top of the C library libcurl, which is known for its high performance and reliability.
One of the main features of Typhoeus is its ability to make parallel requests. This means that it can send multiple requests at the same time, and wait for all of them to finish before returning the results. This can greatly reduce the time it takes to make multiple requests, as it eliminates the need to wait for each request to complete before sending the next one.
In addition to its parallelism feature, Typhoeus also provides a convenient and easy-to-use Ruby interface for making HTTP requests. It supports all of the common HTTP methods (GET, POST, PUT, DELETE, etc.) and allows you to set various request options, such as headers, timeouts, and authentication. It also supports streaming responses, which allows you to process large responses piece by piece, rather than loading the entire response into memory at once.
Typhoeus is also supports HTTP/2 protocol which provides faster load times and reduced network usage. It also supports streaming which is an essential feature for large data transfer.
Typhoeus is well-documented, actively maintained, and has a large and active community of users. It is widely used in the Ruby ecosystem and is a popular choice for building high-performance web scraping and data-gathering applications.
Note that Typhoeus can also be used as an adapter in popular alternative package Faraday.
Highlights
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"
# GET request
Typhoeus.get("www.example.com")
# POST request
Typhoeus.post("www.example.com/posts", body: { title: "test post", content: "this is my test"})
# make parallel requests:
# hydra is a request queue manager
hydra = Typhoeus::Hydra.hydra
# create request object
first_request = Typhoeus::Request.new("http://example.com/posts/1")
# add complete callbacks
first_request.on_complete do |response|
# callbacks can queue new requests
third_url = response.body
third_request = Typhoeus::Request.new(third_url)
hydra.queue third_request
end
second_request = Typhoeus::Request.new("http://example.com/posts/2")
# queue requests:
hydra.queue first_request
hydra.queue second_request
hydra.run # this is a blocking call that returns once all requests are complete