import time
import sys
import paramiko
import socket
import re
import multiprocessing
host = open('/home/user/hosts', 'r')
hosts = host.readlines()
host.close()
def connect_ssh(host, queue):
        try:
            remote_conn_pre = paramiko.SSHClient()

            remote_conn_pre.set_missing_host_key_policy(
            paramiko.AutoAddPolicy())

            remote_conn_pre.connect(host, username=username, password=password, look_for_keys=False, allow_agent=False, timeout=5)
            time.sleep(0.2)

            print("SSH connection established to %s" % host)
            remote_conn = remote_conn_pre.invoke_shell()
            print("Interactive SSH session established")

            ###здесь операции с хостами####

               queue.put({host: output})

        except (socket.gaierror,socket.timeout,TimeoutError):
                print("Could not connect to %s n" % host)
                sys.exit(1)


def send_commands(function):
    processes = []
    queue = multiprocessing.Queue()
    for l in range(len(hosts)):
        p = multiprocessing.Process(target = function, args = (hosts[l], queue))
        p.start()
        processes.append(p)
    for p in processes:
        p.join()

    results = []
    for p in processes:
        results.append(queue.get())
    return results

send_commands(connect_ssh)

Traceback (most recent call last):
  File "/usr/lib/python3.5/multiprocessing/process.py", line 249, in _bootstrap
    self.run()
  File "/usr/lib/python3.5/multiprocessing/process.py", line 93, in run
    self._target(*self._args, **self._kwargs)
  File "scripts/qos_add_mp.py", line 24, in connect_ssh
    remote_conn_pre.connect(host, username=username, password=password, look_for_keys=False, allow_agent=False, timeout=5)
  File "/usr/local/lib/python3.5/dist-packages/paramiko/client.py", line 341, in connect
    server_key = t.get_remote_server_key()
  File "/usr/local/lib/python3.5/dist-packages/paramiko/transport.py", line 670, in get_remote_server_key
    raise SSHException('No existing session')

NUM_PROCESS = 10
queue = multiprocessing.Queue()
results = []

while hosts:
    processes = []
    for _ in range(NUM_PROCESS):
        if not hosts:
            break
        p = multiprocessing.Process(target=function, args=(hosts.pop(), queue))
        p.start()
        processes.append(p)
    for p in processes:
        p.join()
        results.append(queue.get())
return results

import multiprocessing

hosts = 'h1', 'h2', 'h3'

def connect_ssh(host):
    # ...
    return host

if __name__ == '__main__':
    with multiprocessing.Pool(processes=4) as pool:
        results = pool.map(connect_ssh, hosts)
    print(results)