How to use STDIN from subprocess.Popen

Question

How can I implement something like

$ echo "hello" | my_app

with usage of Python's subprocess?

subprocess.Popen() expects a pipe or a file handle for STDIN. But I want to provide STDIN for the called program via a variable. So something like

myinput = "hello"
subprocess.Popen("an_external_programm", stdin=myinput)
….

Have a look at `Popen.communicate()`. Link: https://docs.python.org/3/library/subprocess.html?highlight=subprocess#subprocess.Popen.communicate — elParaguayo, May 31 '16 at 15:56
Can you be clear about your use case? First off you look like you're piping "hello" to your script, in the second example it's a variable in your script. — elParaguayo, May 31 '16 at 15:59
I want to call an external tool from inside my Python script in the kind of the shell example but the content -- the "hello" from shell sxample, is coming from a Python variable. — frlan, May 31 '16 at 16:35

score 1 · Accepted Answer · answered Jun 01 '16 at 07:01

1

I was able to solve my problem by using Popen.communicate()

So some kind of pseudo code:

proc = subprocess.Popen(…)
proc.communicate(input="my_input_via_stdin")

answered Jun 01 '16 at 07:01

frlan

the ellipsis character (...) kind of masks the solution in this answer :-) – matanster Mar 15 '18 at 14:51
What's the answer here? I have the same problem. – O.rka Feb 24 '22 at 09:30

score 0 · Answer 2 · answered May 31 '16 at 15:35

0

In a python script named myscript.py

import sys

for line in sys.stdin:
     print(line)

in unix

echo 'hello' | myscript.py

answered May 31 '16 at 15:35

Seekheart

2 Answers2