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rvestvstreq

MIT 17 1 1,455
629.3 thousand (month) Nov 22 2014 1.0.4(1 year, 7 months ago)
583 13 58 MIT/X
23.11.0(5 months ago) Dec 28 2012 103.4 thousand (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

treq is a Python library for making HTTP requests that provides a simple, convenient API for interacting with web services. It is inspired byt the popular requests library, but powered by Twisted asynchronous engine which allows promise based concurrency.

treq provides a simple, high-level API for making HTTP requests, including methods for GET, POST, PUT, DELETE, etc. It also allows for easy handling of JSON data, automatic decompression of gzipped responses, and connection pooling.

treq is a lightweight library and it's easy to use, it's a good choice for small to medium-sized projects where ease of use is more important than performance.

In web scraping treq isn't commonly used as it doesn't support HTTP2 but it's the only Twisted based HTTP client. treq is also based on callback/errback promises (like Scrapy) which can be easier to understand and maintain compared to asyncio's corountines.

Highlights


uses-twistedno-http2

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"
from twisted.internet import reactor
from twisted.internet.task import react
from twisted.internet.defer import ensureDeferred
import treq

# treq can be used with twisted's reactor with callbacks
response_deferred = treq.get(
    "http://httpbin.org/get"
)
# or POST
response_deferred = treq.post(
    "http://httpbin.org/post",
    json={"key": "value"},  # JSON
    data={"key": "value"},  # Form Data
)

# add callback or errback
def handle_response(response):
    print(response.code)
    response.text().addCallback(lambda body: print(body))
def handle_error(failure):
    print(failure)
# this callback will be called when request completes:
response_deferred.addCallback(handle_response)
# this errback will be called if request fails
response_deferred.addErrback(handle_error)
# this will be called if request completes or fails:
response_deferred.addBoth(lambda _: reactor.stop())  # close twisted once finished

if __name__ == '__main__':
    reactor.run()

#Note that treq can also be used with async/await:
async def main():
    # content reads response data and get sends a get request:
    print(await treq.content(await treq.get("https://example.com/")))

if __name__ == '__main__':
    react(lambda reactor: ensureDeferred(main()))
```

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