About Envoy
Recently I stumble upon Envoy. Envoy is a wrapper around the subprocess module and
is supposed to humanize subprocess of Python.
Its written by Kenneth Reitz (the author of “Requests: HTTP for Humans“)
Why use Envoy?
It was written to be an easy to use alternative to subprocess.
“Envoy: Python Subprocesses for Humans.”
Install Envoy
Envoy is available from PyPI and can be installed with pip.
Search for the Envoy package via the pip command-line tool.
pip search envoy
” envoy – Simple API for running external processes. “Install Envoy
$ pip install envoy
- Add, Remove, and Search Packages in Python with pip
- How to Install Virtualenv (Python)
- How to use Pip and PyPI
Import Envoy
Just like with any other Python modules, we have to import them first.
Start your Python interpreter and type “import envoy”
import envoy
Great, Envoy is imported, now we can start to discover its functions etc.
Envoy Methods and Attributes
After you have imported a module in Python, it’s always good to see what functions, classes and methods that the module provides. One way of doing that is using “dir(envoy)”.
Using dir(module)
That will list the names of all functions and variables, that are defined in the Envoy module.
>>> dir(envoy)
That will give you an output like this:
['Command', 'ConnectedCommand', 'Response', '__builtins__', '__doc__', '__file__', '__name__', '__package__', '__path__', '__version__', 'connect', 'core', 'expand_args', 'os', 'run', 'shlex', 'subprocess', 'threading’]
If you want to get one name per line, just run a simple for loop:
>>> for i in dir(envoy): print i
This output shows you one name per line:
... Command ConnectedCommand Response __builtins__ __doc__ __file__ __name__ __package__ __path__ __version__ connect core expand_args os run shlex subprocess threading >>>
You can also use “help(envoy)” to get the documentation on all the functions.
Envoy Usage
Let’s take a look at the “run” method for Envoy.
envoy.run()
To check the uptime of our machine, we can use the “uptime” command.
r = envoy.run("uptime”)
Standard Output
To see the output, we add “std_out”:
>>> r.std_out '15:11 up 6 days, 1:04, 3 users, load averages: 0.55 0.57 0.61 ‘
Status Code
To get the status code, add “status_code” to your object.
print r.status_code 0
Command
Run a command, get the response:
>>> print r
Standard Error
To get the standard error, add “std_err”.
r.std_err
History
Get history.
r.history [<response 'uptime'="">]
Envoy Examples
Check for the Chrome process
r = envoy.run("ps aux |grep Chrome")
print r.std_out
In our last example, I make use of multiple commands.
import envoy cmd = ['date', "uptime", "w"] r = envoy.run(cmd) print r.std_out
Get the status code of all commands
import envoy
cmd = ['date', "uptime", "w"]
for command in cmd:
r = envoy.run(cmd)
print r.status_code
Get the status code + the output of each command
import envoy
cmd = ['date', "uptime", "w"]
for command in cmd:
r = envoy.run(cmd)
print r.status_code, r.std_out
Envoy has become my main library to handle external command calls.
It was written to be an easy to use alternative to subprocess and the convenience of envoy.run is really great.