将项目添加到列表列表 - Python

Question

I am looking to use the code I have here to match domains to their DNS resolver name

Current CSV output

domain1 dns1 dns2 dns3 \n domain2 dns1 dns2 dns3 \n etc

This is the incorrect format, because it is adding all domains and dns resolvers to the same row, instead of a new row based on the new domain. They are only separated by a blank cell because of the newline character. I instead want it to be written as below, where each domain & its dns resolvers are written to their own individual row.

Expected CSV output:

domain1 dns1 dns2 dns3
domain2 dns1 dns2 dns3
domain3 dns1 dns2 dns3
etc...

I want the CSV file to be written out in the correct format, and with the code that I have, every time a domain is passed to def dns_resolver, it should iterate to a new list index. that way, each domain, and it's dns resolvers have their own list, so when writing out to a new CSV file, each domain will be printed in it's own row in the CSV file.

The code is not iterating through the list index correctly, and does not add the domain & its dns names to any list because of this. When they are written all into the same list, it works fine, but they are written out all into the same row, which is incorrect. So instead of using 1 list, I am going to use a list of lists, and write each to its own list, and then write each list to the csv file, so that they are in their own rows. Normally the domains will be read into a list from a csv file, but for the sake of this, I entered 3 values.

import dns.resolver 
import csv
import os
from os.path import dirname, abspath
r = 0

def dns_resolver(domain):
    server = []
    resolvers = []
    
    try:
        resolvers = dns.resolver.resolve(domain, 'NS')
        #dns_list.append(domain)
        for x in resolvers:
            #dns_list.append(x.target)
            #dns_list.append('\n') 
            server.append(str(x.target))
    except:
        server.append('did not resolve')
    finally:
        return (domain, *server)
            

# Read in all domains from csv file domains.csv & count how many domains there are listed
domain_list = ['google.com', 'facebook.com', 'github.com']
domain_amount = 0

with open(domainFName, 'r') as file:
    for line in csv.reader(file):
        name = (line)
        domain_list.append(line)
        domain_amount += 1

for first_domain in domain_list:
    for x in first_domain:
        outputWriter.writerow(dns_resolver(x))

Answer 1

• You can simply make your dns_resolver function return a list for given domain.
• The *server is a shorthand to append each item into a list.
• Using list comprehension, collect all lists into a list of lists to write to CSV.

def dns_resolver(domain):
    # do your dns resolution
    # server = dns.resolver.resolve(domain, 'NS')
    server = ["dns1", "dns2", "dns3", "dns4"]
    return [domain, *server]
        

# Read in all domains
domain_list = ['google.com', 'facebook.com', 'github.com']

print([dns_resolver(d) for d in domain_list])

Output:

[
   ['google.com', 'dns1', 'dns2', 'dns3', 'dns4'],
   ['facebook.com', 'dns1', 'dns2', 'dns3', 'dns4'],
   ['github.com', 'dns1', 'dns2', 'dns3', 'dns4']
]