Python - how to execute shell commands with pipe, but without 'shell=True'?

While the accepted answer is correct/working, another option would be to use the Popen.communicate() method to pass something to a process' stdin:

>>> import subprocess
>>> p2 = subprocess.Popen(["grep", "-c", "test"], stdin=subprocess.PIPE, stdout=subprocess.PIPE)
>>> p2.communicate("This_is_a_testing")
('1\n', None)
>>> print p2.returncode
0
>>>>

This resolves the need to execute another command just to redirect it's output, if the output is already known in the python script itself.

However communicate has the side-effect, that it waits for the process to terminate. If asynchronous execution is needed/desired using two processes might be the better option.

Please look here:

>>> import subprocess
>>> p1 = subprocess.Popen(["echo", "This_is_a_testing"], stdout=subprocess.PIPE)
>>> p2 = subprocess.Popen(["grep", "-c", "test"], stdin=p1.stdout)
>>> 1
p1.stdout.close()
>>> p2.communicate()
(None, None)
>>>

here you get 1 as output after you write p2 = subprocess.Popen(["grep", "-c", "test"], stdin=p1.stdout), Do not ignore this output in the context of your question.

If this is what you want, then pass stdout=subprocess.PIPE as argument to the second Popen:

>>> p1 = subprocess.Popen(["echo", "This_is_a_testing"], stdout=subprocess.PIPE)
>>> p2 = subprocess.Popen(["grep", "test"], stdin=p1.stdout, stdout=subprocess.PIPE)
>>> p2.communicate()
('This_is_a_testing\n', None)
>>>

>>> import subprocess

>>> mycmd=subprocess.getoutput('df -h | grep home | gawk \'{ print $1 }\' | cut -d\'/\' -f3')

>>> mycmd 

'sda6'

>>>

From the manual:

to get anything other than None in the result tuple, you need to give stdout=PIPE and/or stderr=PIPE

p2 = subprocess.Popen(["grep", "-c", "test"], stdin=p1.stdout, stdout=subprocess.PIPE)