Python: run a bash script with standard input from python

Question

I have a bash script file called g2p which runs as following:

$echo "teststring" | ./g2p @g2pumap=./map.txt

Now I am writing a python script using python 2.6, I need to run this bash script( g2p) inside python.

I checked this answer:Python: subprocess and running a bash script with multiple arguments

I wrote:

import subprocess

val = subprocess.check_call(["./eng_GBR/g2p",  "./map.txt"],  shell=True)

my problem is how to send standard input to g2p (bash script) inside python code, and also I get a bit confused about pass value to @g2pumap argument.

MisterMiyagi · Accepted Answer · 2018-05-09 07:30:02Z

2

The restriction to Python2.6 was added to the question later on. A portable solution is at the end of this answer.

Since Python 3.5, subprocess.run should match most "call program with X" use cases. It's input parameter does what you want:

The input argument is passed to [...] the subprocess’s stdin.

You can feed it a bytes string directly:

import subprocess

g2p_process = subprocess.run(["./eng_GBR/g2p",  "@g2pumap=./map.txt"], input=b'teststring\n')

This is equivalent to your bash call. Note that you must add appropriate newlines (b"\n" at the end) by yourself. Any arguments, such as @g2pumap=./map.txt, can be passed in without escaping.

If you want to have the Exception of check_call, use g2p_process.check_returncode() afterwards.

If you are stuck with an older version or need backwards compatibility, using a bare subprocess.Popen is the most portable. The following should handle your use case:

import subprocess

g2p_process = subprocess.Popen(
    ["./eng_GBR/g2p", "@g2pumap=./map.txt"],
    stdin=subprocess.PIPE,  # allow sending data via STDIN
)
g2p_process.communicate(input="teststring\n")
if g2p_process.returncode != 0:
    raise RuntimeError

Note that you can also capture stdout and stderr if you need to. Use stdout=subprocess.PIPE and/or stderr=subprocess.PIPE in the call to Popen. Doing so lets g2p_process.communicate return a meaningful tuple of (stdoutdata, stderrdata).

See the subprocess.Popen method docs on how to work with such an object. It is usually a good idea to check its returncode, or kill dangling processes. You can also replicate subprocess.run if you feel like it, since it does proper error handling.

edited May 9, 2018 at 7:30

answered May 8, 2018 at 14:52

MisterMiyagi

53.4k14 gold badges131 silver badges138 bronze badges

Sign up to request clarification or add additional context in comments.

5 Comments

Mahsa Over a year ago

Sinec I am using python 2.6.6 , it does not have this attribute, I think I should use "subprocess.call/check_call""

MisterMiyagi Over a year ago

You should point out that version restriction in your question. Python 2.6.6 is seriously outdated.

iBug Over a year ago

I think Python 2.6 is halfway ancient. People only use 2.7 and 3.x nowadays.

chepner Over a year ago

People with a choice use 2.7 or 3.x. But yes, 2.6 is old enough to warrant special mention.

MisterMiyagi Over a year ago

@Zeinab I have added a version that works with Python 2.4 - 3.X.

helloworld · Accepted Answer · 2018-05-08 14:50:58Z

0

import subprocess

value1=...
value2=...
......

val = subprocess.check_call(["path/script.sh",  value1+" "+value2+" "+ .... ],  shell=True)

answered May 8, 2018 at 14:50

helloworld

591 silver badge9 bronze badges

Collectives™ on Stack Overflow

Python: run a bash script with standard input from python

2 Answers 2

5 Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

5 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related