What is the simplest way to SSH using Python?

Your definition of “simplest” is important here – simple code means using a module (though “large external library” is an exaggeration).

I believe the most up-to-date (actively developed) module is paramiko. It comes with demo scripts in the download, and has detailed online API documentation. You could also try PxSSH, which is contained in pexpect. There’s a short sample along with the documentation at the first link.

Again with respect to simplicity, note that good error-detection is always going to make your code look more complex, but you should be able to reuse a lot of code from the sample scripts then forget about it.

You can code it yourself using Paramiko, as suggested above. Alternatively, you can look into Fabric, a python application for doing all the things you asked about:

Fabric is a Python library and
command-line tool designed to
streamline deploying applications or
performing system administration tasks
via the SSH protocol. It provides
tools for running arbitrary shell
commands (either as a normal login
user, or via sudo), uploading and
downloading files, and so forth.

I think this fits your needs. It is also not a large library and requires no server installation, although it does have dependencies on paramiko and pycrypt that require installation on the client.

The app used to be here. It can now be found here.

* The official, canonical repository is git.fabfile.org
* The official Github mirror is GitHub/bitprophet/fabric

There are several good articles on it, though you should be careful because it has changed in the last six months:

Deploying Django with Fabric

Tools of the Modern Python Hacker: Virtualenv, Fabric and Pip

Simple & Easy Deployment with Fabric and Virtualenv

Later: Fabric no longer requires paramiko to install:

$ pip install fabric
Downloading/unpacking fabric
  Downloading Fabric-1.4.2.tar.gz (182Kb): 182Kb downloaded
  Running setup.py egg_info for package fabric
    warning: no previously-included files matching '*' found under directory 'docs/_build'
    warning: no files found matching 'fabfile.py'
Downloading/unpacking ssh>=1.7.14 (from fabric)
  Downloading ssh-1.7.14.tar.gz (794Kb): 794Kb downloaded
  Running setup.py egg_info for package ssh
Downloading/unpacking pycrypto>=2.1,!=2.4 (from ssh>=1.7.14->fabric)
  Downloading pycrypto-2.6.tar.gz (443Kb): 443Kb downloaded
  Running setup.py egg_info for package pycrypto
Installing collected packages: fabric, ssh, pycrypto
  Running setup.py install for fabric
    warning: no previously-included files matching '*' found under directory 'docs/_build'
    warning: no files found matching 'fabfile.py'
    Installing fab script to /home/hbrown/.virtualenvs/fabric-test/bin
  Running setup.py install for ssh
  Running setup.py install for pycrypto
...
Successfully installed fabric ssh pycrypto
Cleaning up...

This is mostly cosmetic, however: ssh is a fork of paramiko, the maintainer for both libraries is the same (Jeff Forcier, also the author of Fabric), and the maintainer has plans to reunite paramiko and ssh under the name paramiko. (This correction via pbanka.)

If you want to avoid any extra modules, you can use the subprocess module to run

ssh [host] [command]

and capture the output.

Try something like:

process = subprocess.Popen("ssh example.com ls", shell=True,
    stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
output,stderr = process.communicate()
status = process.poll()
print output

To deal with usernames and passwords, you can use subprocess to interact with the ssh process, or you could install a public key on the server to avoid the password prompt.

Like hughdbrown, I like Fabric. Please notice that while it implement its own declarative scripting (for making deploys and the such) it can also be imported as a Python module and used on your programs without having to write a Fabric script.

Fabric has a new maintainer and is in the process of being rewriten; that means that most tutorials you’ll (currently) find on the web will not work with the current version. Also, Google still shows the old Fabric page as the first result.

For up to date documentation you can check: http://docs.fabfile.org

I have written Python bindings for libssh2. Libssh2 is a client-side library implementing the SSH2 protocol.

import socket
import libssh2

sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
sock.connect(('exmaple.com', 22))

session = libssh2.Session()
session.startup(sock)
session.userauth_password('john', '******')

channel = session.channel()
channel.execute('ls -l')

print channel.read(1024)

I found paramiko to be a bit too low-level, and Fabric not especially well-suited to being used as a library, so I put together my own library called spur that uses paramiko to implement a slightly nicer interface:

import spur

shell = spur.SshShell(hostname="localhost", username="bob", password="password1")
result = shell.run(["echo", "-n", "hello"])
print result.output # prints hello

You can also choose to print the output of the program as it’s running, which is useful if you want to see the output of long-running commands before it exits:

result = shell.run(["echo", "-n", "hello"], stdout=sys.stdout)

This worked for me

import subprocess
import sys
HOST="IP"
COMMAND="ifconfig"

def passwordless_ssh(HOST):
        ssh = subprocess.Popen(["ssh", "%s" % HOST, COMMAND],
                       shell=False,
                       stdout=subprocess.PIPE,
                       stderr=subprocess.PIPE)
        result = ssh.stdout.readlines()
        if result == []:
                error = ssh.stderr.readlines()
                print >>sys.stderr, "ERROR: %s" % error
                return "error"
        else:
                return result

For benefit of those who reach here googling for python ssh sample.
The original question and answer are almost a decode old now.
It seems that the paramiko has gain a bit of functionalities (Ok. I’ll admit – pure guessing here – I’m new to Python) and you can create ssh client directly with paramiko.

import base64
import paramiko

client = paramiko.SSHClient()

client.set_missing_host_key_policy(paramiko.AutoAddPolicy())
client.connect('192.168.1.1', username='user', password='password')
stdin, stdout, stderr = client.exec_command('cat /proc/meminfo')
for line in stdout:
    print('... ' + line.strip('n'))
client.close()

This code was adapted from demo of https://github.com/paramiko/paramiko
It works for me.

Have a look at spurplus, a wrapper around spur and paramiko that we developed to manage remote machines and perform file operations.

Spurplus provides a check_output() function out-of-the-box:

import spurplus
with spurplus.connect_with_retries(
        hostname='some-machine.example.com', username='devop') as shell:
     out = shell.check_output(['/path/to/the/command', '--some_argument']) 
     print(out)

please refer to paramiko.org, its very useful while doing ssh using python.

import paramiko

import time

ssh = paramiko.SSHClient() #SSHClient() is the paramiko object</n>

#Below lines adds the server key automatically to know_hosts file.use anyone one of the below

ssh.load_system_host_keys() 

ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())

try:

#Here we are actually connecting to the server.

ssh.connect('10.106.104.24', port=22, username='admin', password='')

time.sleep(5)

#I have mentioned time because some servers or endpoint prints there own information after 
#loggin in e.g. the version, model and uptime information, so its better to give some time 
#before executing the command.

#Here we execute the command, stdin for input, stdout for output, stderr for error

stdin, stdout, stderr = ssh.exec_command('xstatus Time')

#Here we are reading the lines from output.

output = stdout.readlines() 

print(output)


#Below all are the Exception handled by paramiko while ssh. Refer to paramiko.org for more information about exception.


except (BadHostKeyException, AuthenticationException,  
    SSHException, socket.error) as e:           

print(e)

host = "test.rebex.net"
port = 22
username = "demo"
password = "password"

command = "ls"

ssh = paramiko.SSHClient()
ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())
ssh.connect(host, port, username, password)

stdin, stdout, stderr = ssh.exec_command(command)
lines = stdout.readlines()
print(lines)

`