Python subprocess check output not working

Question

I’m trying to run my test_script.py in main_script.py with subprocess. test_script.py is a siple sum program, and main_script.py should call it with 2 arguments, and catch output. Here is the code:

test_script.py

a = int(input())
b = int(input())

print(a+b)

main_script.py

import subprocess
subprocess.check_output(['python', 'test_script.py', 2,3])

This is the error im getting:

Traceback (most recent call last):
  File "C:/Users/John/Desktop/main_script.py", line 2, in <module>
    subprocess.check_output(['python', 'test_script.py', 2,3])
  File "C:Python34libsubprocess.py", line 607, in check_output
    with Popen(*popenargs, stdout=PIPE, **kwargs) as process:
  File "C:Python34libsubprocess.py", line 858, in __init__
    restore_signals, start_new_session)
  File "C:Python34libsubprocess.py", line 1085, in _execute_child
    args = list2cmdline(args)
  File "C:Python34libsubprocess.py", line 663, in list2cmdline
    needquote = (" " in arg) or ("t" in arg) or not arg
TypeError: argument of type 'int' is not iterable

Asked By: Nobbie

||

Source

Answer 1

All parts of argument must a string. Do the following instead:

subprocess.check_output(['python', 'test_script.py', "2", "3"])

If this command fails to run, you’ll get an exception. To catch it and see the output:

try:
  subprocess.check_output(['python', 'test_script.py', "2", "3"], stderr=subprocess.STDOUT)
except subprocess.CalledProcessError as e:
  print e.output

Your second script will fail because it’s expecting input from the stdin, while your master script is sending the 2 and 3 as arguments. Investigate sys.argv

Answered By: Alastair McCormack

Answer 2

https://docs.python.org/3/library/subprocess.html#subprocess.check_output

import subprocess                                                                      
subprocess.check_output("python test_script.py", stderr=subprocess.STDOUT, shell=True)

Answered By: Fabio Duran Verdugo

Answer 3

Actually the subprocess check output command only returns the value. So, you need a variable to store it in. So you can try this:

result = subprocess.check_output("python test_script.py", 
 stderr=subprocess.STDOUT, shell=True)
print(result)

Answered By: Syed Fardin

Python subprocess check output not working

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