Unlocking the Power of Web Scraping with Rust

What is Web Scraping?

Web scraping involves gathering data from a webpage in an automated manner. It’s like loading a page in a web browser, but instead of viewing it, you extract the relevant parts. However, web scraping can be tricky due to the unstructured nature of HTML.

Principles of Web Scraping

To scrape effectively, follow these guidelines:

• Be a Good Citizen: Avoid overwhelming web servers with rapid requests, which can lead to denial-of-service (DoS) attacks. Introduce a small delay between requests to prevent this.
• Aim for Robust Solutions: Instead of relying on brittle methods like finding the seventh paragraph element, focus on more stable approaches that can withstand changes to the webpage.
• Validate, Validate, Validate: Verify as much data as possible to ensure accuracy and guard against unexpected changes.

Building a Web Scraper with Rust

Let’s create a web scraper using Rust to gather life expectancy data from the Social Security Administration (SSA).

Feching the Page with reqwest

First, use the reqwest crate to fetch the webpage. We’ll use the blocking API for simplicity.

use reqwest;

fn do_throttled_request(url: &str) -> Result<String, reqwest::Error> {
    let res = reqwest::blocking::get(url)?;
    let body = res.text()?;
    Ok(body)
}

Parsing the HTML with scraper

Next, parse the HTML using the scraper crate.

use scraper::{Html, Selector};

fn parse_page(html: &str) -> Html {
    Html::parse_document(html)
}

fn select_table(html: &Html) -> Vec<_> {
    let selector = Selector::parse("table").unwrap();
    html.select(&selector).collect()
}

Writing the Data to JSON

Finally, write the extracted data to a JSON file using the json crate.

use json::{object, JsonValue};

fn write_data_to_json(data: &JsonValue) -> Result<(), std::io::Error> {
    let mut file = std::fs::File::create("data.json")?;
    file.write_all(data.to_string().as_bytes())?;
    Ok(())
}

By following these steps and using the right tools, you can build a robust web scraper with Rust that extracts valuable data from websites.