Accepts file or stdin and grabs all TLD domains.

extract.py

import sys
import tldextract

def extract_main_domain(url):
    return tldextract.extract(url).registered_domain

if __name__ == '__main__':
    if len(sys.argv) > 1:
        # read from file
        with open(sys.argv[1], 'r') as f:
            for line in f:
                domain = extract_main_domain(line.strip())
                print(domain)
    else:
        # read from stdin
        for line in sys.stdin:
            domain = extract_main_domain(line.strip())
            print(domain)