Scraping Multiple Pages in Elixir with HTTPoison and Floki

Oct 15, 2023 · 4 min read

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:

  • Basic Elixir knowledge
  • Elixir installed
  • HTTPoison and Floki libraries added
  • 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

  • Use a base URL pattern with #{page} placeholder
  • Loop through pages with for
  • Construct each page URL
  • Send request and parse HTML with HTTPoison & Floki
  • Find and extract data using Floki selectors
  • Print or store scraped data
  • 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.

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