How to return a value from a shell script in a python script

Question

I have a python script which requires a value from a shell script.

Following is the shell script (a.sh):

#!/bin/bash
return_value(){
  value=$(///some unix command)
  echo "$value"
}

return_value

Following is the python script:

Import subprocess
answer = Subprocess.call([‘./a.sh’])
print("the answer is %s % answer")

But its not working.The error is "ImportError : No module named subprocess ". I guess my verison (Python 2.3.4) is pretty old. Is there any substitute for subprocess that can be applied in this case??

Ashwini Chaudhary · Accepted Answer · 2013-06-21 15:03:52Z

9

Use subprocess.check_output:

import subprocess
answer = subprocess.check_output(['./a.sh'])
print("the answer is {}".format(answer))

help on subprocess.check_output:

>>> print subprocess.check_output.__doc__
Run command with arguments and return its output as a byte string.

Demo:

>>> import subprocess
>>> answer = subprocess.check_output(['./a.sh'])
>>> answer
'Hello World!\n'
>>> print("the answer is {}".format(answer))
the answer is Hello World!

a.sh :

#!/bin/bash
STR="Hello World!"
echo $STR

answered Jun 21, 2013 at 15:03

Ashwini Chaudhary

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4 Comments

user2475677 Over a year ago

thanks ashwini for the answer.. The statement inside the python script is not actually a print statment but a cvs command. I had simplified it just for the sake of asking. So in that case can we use {} for interpolating the answer variable or we need to use %s ???

Ashwini Chaudhary Over a year ago

@user2475677 str.format is called new-style string formatting, if you're using string formatting only then both options are fine.

user2475677 Over a year ago

Thanks a lot ashwini, but I just realised that , my version of Python (2.3.4) is pretty old!! It does not have "subprocess"

Nikhil Over a year ago

What if this "a.sh" script is an interactive script which prompts user few question. In that case how can we capture those values in python script...?

Krab · Accepted Answer · 2013-06-21 14:57:37Z

3

use Subprocess.check_output instead of Subprocess.call.

Subprocess.call returns return code of that script.
Subprocess.check_output returns byte stream of script output.

Subprocess.check_output on python 3.3 doc site

answered Jun 21, 2013 at 14:57

Krab

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