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rvestvshttpx

MIT 17 1 1,455
629.3 thousand (month) Nov 22 2014 1.0.4(1 year, 7 months ago)
12,154 12 53 BSD
0.27.0(a month ago) Jul 26 2019 55.4 million (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

httpx is a fully featured HTTP client for Python 3, which provides sync and async APIs, and support for both HTTP/1.1 and HTTP/2. It is designed to be a replacement for the popular requests package, with the added benefit of being fully compatible with Python 3's async features.

One of the main features of httpx is its support for asynchronous programming. This means that it can send multiple requests at the same time, without blocking the execution of your program. This can lead to significant performance improvements, especially when working with many small requests, or when dealing with slow or unreliable network connections.

httpx also supports sending HTTP/2 requests, which allows for more efficient use of network resources and can result in faster page loads.

One of the strengths of httpx is the possibility of working on streaming mode for the response data. This means you can process the response as it comes in, instead of waiting for the entire response to be received. This is useful when working with large files, or when you need to process the data in real-time.

Additionally, httpx provides a number of other features that are common in modern HTTP clients, such as support for sending and receiving cookies, handling redirects, and working with multipart file uploads. It also include support for several well-known authentication modules like BasicAuth, DigestAuth, and BearerAuth.

Highlights


asynciotriosynchttp2

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"
import httpx

# Just like requests httpx can be used directly
response = httpx.get("http://webscraping.fyi/")
response.status_code
200
response.text
"text"
response.content
b"bytes"

# HTTP2 needs to be enabled explicitly and is recommended for web scraping:
response = httpx.get("http://webscraping.fyi/", http2=True)

# httpx can automatically convert json responses to Python dictionaries:
response = httpx.get("http://httpbin.org/json")
print(response.json())
{'slideshow': {'author': 'Yours Truly', 'date': 'date of publication', 'slides': [{'title': 'Wake up to WonderWidgets!', 'type': 'all'}, {'items': ['Why <em>WonderWidgets</em> are great', 'Who <em>buys</em> WonderWidgets'], 'title': 'Overview', 'type': 'all'}], 'title': 'Sample Slide Show'}}

# for POST request it can ingest Python's dictionaries as JSON:
response = requests.post("http://httpbin.org/post", json={"query": "hello world"})
# or form data:
response = requests.post("http://httpbin.org/post", data={"query": "hello world"})

# persistent client can be established using Client object
# this allows to set default values and automatically track cookies
from httpx import Client

c = Client(headers={"User-Agent": "webscraping.fyi"}, http2=True)
c.get('http://httpbin.org/cookies/set/foo/bar')
print(c.cookies['foo'])
'bar'
print(c.get('http://httpbin.org/cookies').json())
{'cookies': {'foo': 'bar'}}

# for asynchronous requests AsyncClient must be used:
import asyncio
from httpx import AsyncClient 

async def example_use():
    async with AsyncClient(headers={"User-Agent": "webscraping.fyi"}) as client:
        response = await client.get("http://httpbing.org/get")
        # to schedule multiple requests concurrently use asyncio gather or as_completed
        three_concurrent_responses = await asyncio.gather(
            client.get("http://httpbing.org/get"),
            client.get("http://httpbing.org/get"),
            client.get("http://httpbing.org/get"),
        )

asyncio.run(example_use())

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