Reraise exception from subprocess

Question

I have code executing in a subprocess that is supposed to raise an exception.

I would like to raise the same exception in the main process when the exception is returned from the subprocess (preferably while preserving the stack trace) but I am not sure how to do this.

I capture the stderr from the subprocess just fine but I can't find how to parse it so I get the type of exception. How would I accomplish this?

I am using python 2.7

main method

import subprocess

example=subprocess.Popen(["python","example.py"],
                                    stdout = subprocess.PIPE,
                                    stderr = subprocess.PIPE)
return_obj, return_error = example.communicate()

if return_error:
# replace with error from subprocess
  print "Should raise ",NameError('HiThere')
  raise TypeError('Wrong type')

subprocess

raise NameError('HiThere')

Answer 1

If all you want is your python code running in a separate process, you should probably not use subprocess. As Serge Ballesta said, subprocess' purpose is to run a different program at the OS level, without particularly caring for what it is - there's nothing to help you properly handle the intricacies of a python interpreter process.

For this kind of purpose, it's probably best to simply import your code and use multiprocessing, which exposes a high-level interface to help you run python code in multiple processes.

Assuming you have a well defined main function on example.py:

from examply import main as example_main
import multiprocessing
pool= multiprocessing.Pool(1)
pool.apply( example_main )

Using this code, both exceptions and return values will be transparently given to your main process.

You can also use Pool.apply_async, if you don't want to block waiting for the result.