Resolve IP address for each hostname from file and save it to the new file.

resolver.py

import dns.resolver
with open('hostnames.txt', 'r') as file, open('result_resovle.csv', 'wb') as outfile:
    for line in file:
        try:
            answers = dns.resolver.query(line.strip(), 'A')
            for rdata in answers:
                outfile.write(line.strip() + ':' + rdata.to_text() + '\n')
        except:
            outfile.write(line.strip() + '\n')