Your Python script takes six hours to log in to 2,000 devices. How do you make it fast and safe?

import os
from concurrent.futures import ThreadPoolExecutor, as_completed

from netmiko import ConnectHandler
from netmiko.exceptions import NetmikoAuthenticationException, NetmikoTimeoutException

USER = os.environ["NET_USER"]
PASSWORD = os.environ["NET_PASS"]

def get_uptime(host):
    device = {"device_type": "cisco_ios", "host": host,
              "username": USER, "password": PASSWORD}
    with ConnectHandler(**device) as conn:
        return conn.send_command("show version | include uptime")

with open("hosts.txt") as f:
    hosts = [line.strip() for line in f if line.strip()]

results, failures = {}, {}
with ThreadPoolExecutor(max_workers=30) as pool:
    futures = {pool.submit(get_uptime, h): h for h in hosts}
    for fut in as_completed(futures):
        host = futures[fut]
        try:
            results[host] = fut.result()
        except (NetmikoTimeoutException, NetmikoAuthenticationException) as exc:
            failures[host] = type(exc).__name__

print(f"{len(results)} ok, {len(failures)} failed")

from nornir import InitNornir
from nornir_netmiko.tasks import netmiko_send_command
from nornir_utils.plugins.functions import print_result

nr = InitNornir(config_file="config.yaml")
result = nr.filter(site="dc1").run(task=netmiko_send_command,
                                   command_string="show version")
print_result(result)
print(sorted(result.failed_hosts))