Handy utility function to get output of shell command piping input to stdin (requires Python 3.5+).

gistfile1.txt

>>> pipe('md5sum', 'This is a test')
--> 'ce114e4501d2f4e2dcea3e17b546f339  -\n'

>>> pipe('md5sum', b'This is a test')
--> b'ce114e4501d2f4e2dcea3e17b546f339  -\n'

>>> pipe(['gzip', '-c'], b'This is a test')
b'\x1f\x8b\x08\x00\xd6\x91\x13Z\x00\x03\x0b\xc9\xc8,V\x00\xa2D\x85\x92\xd4\xe2\x12\x002\x9fz\xc0\x0e\x00\x00\x00'

>>> pipe('bash', 'ls').splitlines()
--> ['pipe.py', 'test.txt']

>>> pipe('bash', 'ls foo', env={'LANG': 'en'})
ls: cannot access 'foo': No such file or directory
--> ''

>>> pipe('bash', 'ls foo', stderr='drop')
--> ''

>>> pipe('bash', 'ls foo', stderr='capture', env={'LANG': 'en'})
--> ('', "ls: cannot access 'foo': No such file or directory\n")

>>> pipe('bash', 'ls foo', stderr='redirect', env={'LANG': 'en'})
--> "ls: cannot access 'foo': No such file or directory\n"

pipe.py

"""Get output of shell command piping input to stdin."""

from subprocess import DEVNULL, PIPE, run, STDOUT

def pipe(cmd, input='', stderr=None, **kwargs):
    kwargs['stdout'] = PIPE
    kwargs['stderr'] = {'redirect': STDOUT, 'capture': PIPE, 'drop': DEVNULL}.get(stderr, stderr)
    kwargs.setdefault('encoding', 'utf-8' if isinstance(input, str) else None)
    res = run(cmd, input=input, **kwargs)
    return (res.stdout, res.stderr) if stderr == 'capture' else res.stdout