from subprocess import run¶
Python’s standard subprocess module provides most of the capabilities you need to run external processes from Python, but the API is thoroughly misleading. It requires you to check documentation every time when you are trying to do really basic things related to creating external processes.
The subprocess.run extension was create to run processes in a polite way.
Walkthrough¶
$ > pip install subprocess.run
To install the package.
>>> from subprocess import run
If installation went successful, import run from subprocess module.
>>> run('uname -v').stdout
'#19-Ubuntu SMP Wed Oct 9 16:20:46 UTC 2013'
The standard output (successful command output) is available thought the stdout attribute.
>>> run('uname -v').status
0
You can access execution status through status attribute.
>>> run('rm not_existing_directory').stderr
'rm: cannot remove `not_existing_directory': No such file or directory'
If something went not so well, the error output is available thought the stderr attribute.
>>> run('ls -la', 'wc -l').stdout
14
If pipe is needed, just add more one after another. Example above is the same as ls -la | wc -l.
>>> run('ls -la', 'wc -l', 'wc -c').stdout
3
And more pipe.
>>> run('wc -c', data="test").stdout
And even more pipe. But this time, the call will take data from python script. This would be roughly something like echo test | wc -c
>>> run('ls -la').stdout.lines
['total 20',
'drwxrwxr-x 3 user user 4096 Dec 20 22:55 .',
'drwxrwxr-x 5 user user 4096 Dec 20 22:57 ..',
'drwxrwxr-x 2 user user 4096 Dec 20 22:37 dir',
'-rw-rw-r-- 1 user user 0 Dec 20 22:52 file']
To help with output processing, both stdout and stderr outputs are equipped with lines attribute, it will help with slicing your output to a list of strings.
>>> run('ls -la').stdout.qlines
[
['total 20']
['drwxrwxr-x', '3', 'user', 'user', '4096', 'Dec', '20', '22:55', '.'],
['drwxrwxr-x', '5', 'user', 'user', '4096', 'Dec', '20', '22:57', '..'],
['drwxrwxr-x', '2', 'user', 'user', '4096', 'Dec', '20', '22:37', 'dir'],
['-rw-rw-r--', '1', 'user', 'user', '0', 'Dec', '20', '22:52', 'file']
]
And with qlines, to split lines to words.
>>> run('ls -la', 'wc -l', 'wc -c').chain
Will return list of executed calls. Then let’s do something that actually make sens
>>> [call.status for call in run('ls -la', 'wc -l', 'wc -c').chain]
[0, 0, 0]
This will return list of statuses inside chain.
>>> [call.stdout for call in run('ls -la', 'wc -l', 'wc -c').chain]
['total 20\ndrwxrwxr-x 3 user user 4096 Dec 20 22:55 .\ndrwxrwxr-x 5 user user 4096 Dec 20 22:57 ..',
'95',
'2']
This will return list of stdouts for commands inside chain.
from subprocess import run
run('grep something', data=run.stdin)
$ ps aux | python script.py
To read from shell pipe.
Status¶
The codebase is less than 100 LOC, feel free to look at it and explain to me why I should/shouldn’t do things this way. Library seems to be pretty stable, feel free to use it as you want.
Source Code¶
Supported platforms¶
- Python2.6
- Python2.7
- Python3.3
- PyPy2.1
