How do I ensure my web scraping with urllib3 respects robots.txt?

To ensure your web scraping activities with urllib3 respect robots.txt, you need to parse the robots.txt file and check the rules before making any requests to the server. The robots.txt file contains rules that define which paths on a server web crawlers are allowed or disallowed from accessing.

Unfortunately, urllib3 does not have built-in functionality for parsing robots.txt. However, you can use Python's urllib.robotparser module to interpret robots.txt and then use urllib3 to make web requests where allowed.

Here is an example of how to do this:

import urllib.robotparser
import urllib3

# Initialize urllib3 PoolManager
http = urllib3.PoolManager()

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

# Parse the robots.txt file
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(url):
    return rp.can_fetch('*', url)

# Function to scrape a URL if allowed by robots.txt
def scrape_url(url):
    if is_allowed(url):
        response = http.request('GET', url)
        # Process the response
        print(response.status)
        print(response.data)
    else:
        print(f"Scraping blocked by robots.txt: {url}")

# Example usage
scrape_url(base_url + 'some-page/')

This example does the following:

1. Initializes a urllib3.PoolManager instance for making HTTP requests.
2. Sets the base URL of the website you want to scrape.
3. Uses urllib.robotparser.RobotFileParser to parse the robots.txt file from the website.
4. Defines a function is_allowed that checks if a URL is allowed by robots.txt.
5. Defines a function scrape_url that scrapes a URL if it is allowed by robots.txt. It prints the status and data of the HTTP response if allowed, or a message indicating that scraping is blocked by robots.txt.

Remember to follow these guidelines when scraping:

• Always read and comply with robots.txt.
• Do not make requests too frequently; add delays between requests to avoid overloading the server.
• Check the website's terms of service to ensure you're allowed to scrape it.
• Be prepared to handle any legal implications of scraping a website.

Please note that respecting robots.txt is a matter of etiquette and not enforced by law in many regions. However, failing to follow robots.txt can lead to your IP being banned from accessing the site.