A lot of confusion and I can't seem to solve this issue

[snippsat]

Now the only problem I am facing is how to output the scan result in a text file like scan.txt

You can do it like this.

import requests

with open('ip_lst1.txt') as fd,open('scan.txt', 'w') as fd_out:
    for ip in fd:
        try:
            ip = ip.strip()
            print(ip)
            response = requests.get(f"http://{ip}:9200/_cat/indices", timeout=2)
            print(response.text.strip())
            fd_out.write(f'{ip}\n{response.text.strip()}\n')
        except Exception as error:
            #print(error)
            pass