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rvestvsaiohttp

MIT 17 1 1,455
629.3 thousand (month) Nov 22 2014 1.0.4(1 year, 7 months ago)
14,508 30 499 Apache 2
3.9.3(2 months ago) Jul 26 2019 105.3 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

aiohttp is an asynchronous HTTP client/server framework for asyncio and Python. It provides a simple API for making HTTP requests and handling both client and server functionality. Like the requests package, aiohttp is designed to be easy to use and handle many of the low-level details of working with HTTP.

The main benefit of aiohttp over requests is that it is built on top of the asyncio library, which means that it can handle many requests at the same time without blocking the execution of your program. This can lead to significant performance improvements when making many small requests, or when dealing with slow or unreliable network connections.

aiohttp provides both client and server side functionality, so you can use it to create web servers and handle client requests in a non-blocking manner. It also supports WebSocket protocol, so it can be used for building real-time application like chat, game, etc.

aiohttp also provide several features for handling connection errors, managing timeouts, and client sessions. It also provide similar features like requests package like redirect handling, cookies, and support for several authentication modules.

You can install aiohttp via pip package manager:

pip install aiohttp

In terms of API design, aiohttp is similar to requests and thus should be familiar to anyone who has used the requests library, but it provides an async with block to manage the context of the connection and used await statement to wait for the result.

It''s worth noting that aiohttp is built on top of asyncio and is designed to be used in Python 3.5 and above. It provides the same functionality as httpx but it is specifically built for the asyncio framework.

Highlights


asynciowebsocketshttp2http-servermulti-partresponse-streaminghttp-proxy

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 asyncio
from aiohttp import ClientSession, WSMsgType

# aiohttp only provides async client so we must use a coroutine:
async def run():
    async with ClientSession(headers={"User-Agent": "webscraping.fyi"}) as session:
        # we can use the session to make requests:
        response = await session.get("http://httpbin.org/headers")
        print(response.status)
        # note: to read the response body we must use await:
        print(await response.text())

        # aiohttp also comes with convenience methods for common requests:
        # POST json
        resp = await session.post("http://httpbin.org/post", json={"key": "value"})
        # POST form data
        resp = await session.post("http://httpbin.org/post", data={"key": "value"})
        # decode response as json
        resp = await session.get("http://httpbin.org/json")
        data = await resp.json()
        print(data)

        # aiohttp also supports websocket connections
        # which can be used to scrape websites that use websockets:
        async with session.ws_connect("http://example.org/ws") as ws:
            async for msg in ws:
                if msg.type == WSMsgType.TEXT:
                    if msg.data == "close cmd":
                        await ws.close()
                        break
                    else:
                        await ws.send_str(msg.data + "/answer")
                elif msg.type == WSMsgType.ERROR:
                    break


asyncio.run(run())

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