Python: Getting a traceback from a multiprocessing.Process

Question

I am trying to get hold of a traceback object from a multiprocessing.Process. Unfortunately passing the exception info through a pipe does not work because traceback objects

Answer 1

This is a variation of this excellent answer. Both are relying on tblib for storing the traceback.

However, instead of having to return the exception object (as asked for by the OP), the worker function can be left as-is and is just wrapped in try/except to store exceptions for re-raise.

import tblib.pickling_support
tblib.pickling_support.install()

import sys

class DelayedException(Exception):

    def __init__(self, ee):
        self.ee = ee
        __,  __, self.tb = sys.exc_info()
        super(DelayedException, self).__init__(str(ee))

    def re_raise(self):
        raise self.ee, None, self.tb

Example

def worker():
    try:
        raise ValueError('Something went wrong.')
    except Exception as e:
        raise DelayedException(e)


if __name__ == '__main__':

    import multiprocessing

    pool = multiprocessing.Pool()
    try:
        pool.imap(worker, [1, 2, 3])
    except DelayedException as e:
        e.re_raise()