How do I set up MechanicalSoup to respect robots.txt rules?

MechanicalSoup is a Python library for automating interaction with websites. It does not have built-in support for parsing and respecting robots.txt rules. However, you can use the robotparser module, which is included in the Python standard library, to read and parse the robots.txt file for a website, and then use MechanicalSoup accordingly to respect the rules specified in that file.

Here's how you can combine robotparser and MechanicalSoup to respect robots.txt rules:

import mechanicalsoup
import urllib.robotparser

# URL of the website you want to scrape
base_url = "http://example.com"

# Initialize the parser for robots.txt
rp = urllib.robotparser.RobotFileParser()
rp.set_url(base_url + "/robots.txt")
rp.read()

# Function to check if a URL is allowed by robots.txt
def is_allowed_by_robots(url):
    return rp.can_fetch("*", url)

# Initialize MechanicalSoup browser
browser = mechanicalsoup.StatefulBrowser()

# Example URL you want to scrape
url_to_scrape = base_url + "/some-page"

# Check if scraping the URL is allowed
if is_allowed_by_robots(url_to_scrape):
    # Use MechanicalSoup to scrape the page
    response = browser.open(url_to_scrape)
    page = response.text
    # ... perform your scraping task
else:
    print(f"Scraping {url_to_scrape} is disallowed by robots.txt")

# Don't forget to close the browser session
browser.close()

In the example above, we first set up the robotparser to read from the robots.txt file of the target website. We define a helper function is_allowed_by_robots() to check if a given URL can be fetched according to the robots.txt rules.

Before making requests with MechanicalSoup, we use this helper function to ensure that we're allowed to scrape the particular webpage. If robots.txt disallows the URL, we avoid scraping it.

Please note that the robots.txt file is a convention to tell well-behaved crawlers which parts of the site should not be crawled. It's up to the developer to implement a crawler that respects these rules. Some websites might have additional terms of service that regulate scraping, which are not expressed in robots.txt, so it's always best to check a website's terms of service to ensure compliance with their policies before scraping.

Finally, it is important to be ethical and considerate when scraping websites, so as to not overload servers with too many requests in a short amount of time. Use appropriate rate limiting and try to minimize the load you impose on the website's server.

MechanicalSoup does not have built-in rate limiting, but you can implement it yourself with time.sleep() between requests or by using more sophisticated approaches like the ratelimiter package or other similar utilities.