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rvestvsscrapyd

MIT 17 1 1,455
629.3 thousand (month) Nov 22 2014 1.0.4(1 year, 7 months ago)
2,833 7 31 BSD
1.4.3(6 months ago) Sep 04 2013 331.5 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

Scrapyd is a service for running Scrapy spiders. It allows you to schedule spiders to run at regular intervals and also allows you to run spiders on remote machines. It is built in Python, and it is meant to be used in a server-client architecture, where the scrapyd server runs on a remote machine, and clients can schedule and control spider runs on the server using an HTTP API. With Scrapyd, you can schedule spider runs on a regular basis, schedule spider runs on demand, and view the status of running spiders.

You can also see the logs of completed spiders, and manage spider settings and configurations. Scrapyd also provides an API that allows you to schedule spider runs, cancel spider runs, and view the status of running spiders. You can install the package via pip by running pip install scrapyd and then you can run the package by running scrapyd command in your command prompt. By default, it will start a web server on port 6800, but you can specify a different port using the `--port`` option.

Scrapyd is a good solution if you need to run Scrapy spiders on a remote machine, or if you need to schedule spider runs on a regular basis. It's also useful if you have multiple spiders, and you need a way to manage and monitor them all in one place.

for more web interface see scrapydweb

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"
$ scrapyd
$ curl http://localhost:6800/schedule.json -d project=myproject -d spider=spider2

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