Saving the print result in a text file

[snippsat]

where do I insert this line of code?

You should learn to test out code when get solutions.
It's after results(you make a set) line 30 in your code.
Both mine and perfringo(a little fancier🎈) code dos the same.

# Make a test set
results = {'1.255.255.254', '2.255.255.254', '3.255.255.254'}

with open('ip_out.csv', 'w') as fp:
    print(*results, sep='\n', file=fp)

with open('ip_out1.csv', 'w') as fp:
    for ip in results:
        fp.write(f'{ip}\n')

In files,and Sets dos not have order.

Output:
2.255.255.254
3.255.255.254
1.255.255.254