Scraping Multiple Pages in Elixir with HTTPoison and Floki

Web scraping is useful to programmatically extract data from websites. Often you need to scrape multiple pages from a site to gather complete information. In this article, we'll see how to scrape multiple pages in Elixir using the HTTPoison and Floki libraries.

Prerequisites

To follow along, you'll need:

def deps do
  [
    {:httpoison, "~> 1.8"},
    {:floki, "~> 0.30.0"}
  ]
end

Import Libraries

We'll need the following imports:

import HTTPoison
import Floki

Define Base URL

—

We'll scrape a blog - https://copyblogger.com/blog/. The page URLs follow a pattern:

<https://copyblogger.com/blog/>
<https://copyblogger.com/blog/page/2/>
<https://copyblogger.com/blog/page/3/>

Let's define the base URL pattern:

base_url = "<https://copyblogger.com/blog/page/#{page}/>"

The #{page} allows us to insert the page number.

Specify Number of Pages

Next, we'll specify how many pages to scrape. Let's scrape the first 5 pages:

num_pages = 5

Loop Through Pages

We can now loop from 1 to num_pages and construct the URL for each page:

for page <- 1..num_pages do

  # Construct URL
  url = String.replace(base_url, "#{page}", to_string(page))

  # Code to scrape each page

end

Send Request and Parse HTML

Inside the loop, we'll send a GET request and parse the HTML:

{:ok, response} = HTTPoison.get(url)

html = response.body |> Floki.parse_document

This gives us a parsed HTML document to extract data from.

Extract Data

Now within the loop we can use Floki selectors to find and extract data from each page:

html
|> Floki.find("article")
|> Enum.each(fn(article) ->

  # Extract data from article tag

  title = Floki.find(article, "h2.entry-title") |> Floki.text
  url = Floki.find(article, "a.entry-title-link") |> Floki.attribute("href")
  author = Floki.find(article, "div.post-author a") |> Floki.text

end)

Full Code

Our full code to scrape 5 pages is:

import HTTPoison
import Floki

base_url = "https://copyblogger.com/blog/page/#{page}/"
num_pages = 5

for page <- 1..num_pages do

  url = String.replace(base_url, "#{page}", to_string(page))

  {:ok, response} = HTTPoison.get(url)

  html = response.body |> Floki.parse_document

  html
  |> Floki.find("article")
  |> Enum.each(fn(article) ->

    title = Floki.find(article, "h2.entry-title") |> Floki.text
    url = Floki.find(article, "a.entry-title-link") |> Floki.attribute("href")
    author = Floki.find(article, "div.post-author a") |> Floki.text
    
    categories = Floki.find(article, "div.entry-categories a") |> Enum.map(&Floki.text/1)

    IO.puts "Title: #{title}"
    IO.puts "URL: #{url}"
    IO.puts "Author: #{author}" 
    IO.puts "Categories: #{inspect(categories)}"

  end)

end

This allows us to scrape and extract data from multiple pages sequentially. The code can be extended to scrape any number of pages.

Summary

Web scraping enables collecting large datasets programmatically. With the techniques here, you can scrape and extract information from multiple pages of a website in Elixir.

While these examples are great for learning, scraping production-level sites can pose challenges like CAPTCHAs, IP blocks, and bot detection. Rotating proxies and automated CAPTCHA solving can help.

Proxies API offers a simple API for rendering pages with built-in proxy rotation, CAPTCHA solving, and evasion of IP blocks. You can fetch rendered pages in any language without configuring browsers or proxies yourself.

This allows scraping at scale without headaches of IP blocks. Proxies API has a free tier to get started. Check out the API and sign up for an API key to supercharge your web scraping.

With the power of Proxies API combined with Python libraries like Beautiful Soup, you can scrape data at scale without getting blocked.