Use paramiko and create simple ssh and ssh-nat tunnel connection

ssh_login.py

from ssh_tunnel import SSH
client = SSH("1.2.3.4", keyfile="/home/user/.ssh/id_rsa", username="user").client

stdin, stdout, stderr = client.exec_command("hostname")
for line in stdout.readlines():
    print lines

ssh_tunnel.py

import paramiko

class SSH():
    def __init__(self, server_ip=None, nat_ip=None,
                 keyfile=None, username=None, server_port=None, nat_port=None):

        self.server_ip = server_ip
        self.server_port = server_port if server_port else 22

        self.nat_ip = nat_ip
        self.nat_port = nat_port if nat_port else 22

        self.keyfile = keyfile
        self.username = username

        self.public_client = None
        self.private_client = None
        self.client = self.server_ssh()
        if self.nat_ip:
            self.client = self.tunnel_ssh()


    def get_client(self):
        p = paramiko.SSHClient()
        p.set_missing_host_key_policy(paramiko.AutoAddPolicy())
        return p


    def server_ssh(self):
        client = self.get_client()
        # Nat or Server?
        public_ip = self.server_ip
        port = self.server_port
        if self.nat_ip:
            public_ip = self.nat_ip
            port = self.nat_port
        client.connect(
            public_ip,
            port,
            username=self.username,
            key_filename=self.keyfile,
            timeout=15)
        self.public_client = client
        return client


    def tunnel_ssh(self):
        destaddr = (self.server_ip, self.server_port)
        proxy_addr = ('127.0.0.1', 4445)
        transport = self.public_client.get_transport()
        channel = transport.open_channel("direct-tcpip", destaddr, proxy_addr)
        client = self.get_client()
        client.connect(
            'localhost',
            4445,
            username=self.username,
            key_filename=self.keyfile,
            sock=channel,
            timeout=15)

        self.private_client = client
        return client