CODEWITHSUNDEEP
pythonpython-3.xsubprocess
verkter
verkter

Reputation: 778

Return full error message from subprocess

I would like to get a full, descriptive error message from failed Python script executed with subprocess module.

I have a following script sub_script.py which fails and produces IndexError: pop from empty list error when executed on it's own:

# sub_script.py

empty_list = []
empty_list.pop()

I am calling sub_script.py from sub_test.py as follows:

# sub_test.py

import subprocess
import sys

print(str(subprocess.run([sys.executable, 'sub_script.py'],
                         check=True,
                         capture_output=True)))

However I am only getting subprocess.CalledProcessError error.

Traceback (most recent call last):
  File "/Users/my_user/Desktop/my_dir/sub_test.py", line 4, in <module>
    print(str(subprocess.run([sys.executable, 'sub_script.py'],
  File "/usr/local/Cellar/[email protected]/3.9.5/Frameworks/Python.framework/Versions/3.9/lib/python3.9/subprocess.py", line 528, in run
    raise CalledProcessError(retcode, process.args,
subprocess.CalledProcessError: Command '['/usr/local/opt/[email protected]/bin/python3.9', 'sub_script.py']' returned non-zero exit status 1.

I would like to see a full description of the error returned from sub_script.py (IndexError: pop from empty list) when it's executed with a subprocess in sub_test.py.

Is it possible to get full error when script executes and fails within subprocess.run?

Upvotes: 0

Views: 2587

Answers (1)

Lenormju
Lenormju

Reputation: 4368

Keep the return value of the subprocess.run call instead of immediately converting it to a str, and do not have check=True.

# main.py
import subprocess
import sys

command = [sys.executable, 'task.py']
outcome = subprocess.run(command, check=False, capture_output=True)
print(f"returncode = {outcome.returncode}")
if outcome.returncode != 0:
    # there was an error, we assume the traceback was printed to stderr
    print("there was an error :\n")
    print(outcome.stderr.decode("utf-8"))

# task.py
empty_list = []
empty_list.pop()

output :

returncode = 1
there was an error :

Traceback (most recent call last):
  File "task.py", line 2, in <module>
    empty_list.pop()
IndexError: pop from empty list

Upvotes: 2

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