How to run " ps cax | grep something " in Python?

See Replacing shell pipeline:

import subprocessproc1 = subprocess.Popen(['ps', 'cax'], stdout=subprocess.PIPE)proc2 = subprocess.Popen(['grep', 'python'], stdin=proc1.stdout,                         stdout=subprocess.PIPE, stderr=subprocess.PIPE)proc1.stdout.close() # Allow proc1 to receive a SIGPIPE if proc2 exits.out, err = proc2.communicate()print('out: {0}'.format(out))print('err: {0}'.format(err))

PS. Using shell=True can be dangerous. See for example the warning in the docs.

There is also the sh module which can make subprocess scripting in Python a lot more pleasant:

import shprint(sh.grep(sh.ps("cax"), 'something'))

You've already accepted an answer, but:

Do you really need to use grep? I'd write something like:

import subprocessps = subprocess.Popen(('ps', 'cax'), stdout=subprocess.PIPE)output = ps.communicate()[0]for line in output.split('\n'):    if 'something' in line:        ...

This has the advantages of not involving shell=True and its riskiness, doesn't fork off a separate grep process, and looks an awful lot like the kind of Python you'd write to process data file-like objects.

import subprocessprocess = subprocess.Popen("ps cax | grep something",                             shell=True,                             stdout=subprocess.PIPE,                           )stdout_list = process.communicate()[0].split('\n')