Problems with multiprocessing

Question

I'm trying to implement a python script which reads the content of a pdf file and move that file to a specific directory. On my Debian machine it works without any problem. But on my Xubuntu system I"m getting the following error:

Traceback (most recent call last):
File "/usr/lib/python3.6/threading.py", line 916, in _bootstrap_inner
  self.run()
File "/usr/lib/python3.6/threading.py", line 864, in run
  self._target(*self._args, **self._kwargs)
File "/usr/lib/python3.6/multiprocessing/pool.py", line 463, in _handle_results
  task = get()
File "/usr/lib/python3.6/multiprocessing/connection.py", line 251, in recv
  return _ForkingPickler.loads(buf.getbuffer())
TypeError: __init__() takes 1 positional argument but 2 were given

At this point, the script halts until I cancel it with KeyboardInerrupt, which gives me the rest of the error:

Process ForkPoolWorker-5:
Process ForkPoolWorker-6:
Process ForkPoolWorker-3:
Traceback (most recent call last):
Traceback (most recent call last):
  File "/usr/lib/python3.6/multiprocessing/process.py", line 258, in _bootstrap
    self.run()
  File "/usr/lib/python3.6/multiprocessing/process.py", line 258, in _bootstrap
    self.run()
  File "/usr/lib/python3.6/multiprocessing/process.py", line 93, in run
    self._target(*self._args, **self._kwargs)
  File "/usr/lib/python3.6/multiprocessing/process.py", line 93, in run
    self._target(*self._args, **self._kwargs)
  File "/usr/lib/python3.6/multiprocessing/pool.py", line 108, in worker
    task = get()
  File "/usr/lib/python3.6/multiprocessing/pool.py", line 108, in worker
    task = get()
Traceback (most recent call last):
  File "/usr/lib/python3.6/multiprocessing/queues.py", line 334, in get
    with self._rlock:
  File "/usr/lib/python3.6/multiprocessing/queues.py", line 334, in get
    with self._rlock:
  File "/usr/lib/python3.6/multiprocessing/synchronize.py", line 95, in __enter__
    return self._semlock.__enter__()
  File "/usr/lib/python3.6/multiprocessing/synchronize.py", line 95, in __enter__
    return self._semlock.__enter__()
KeyboardInterrupt
KeyboardInterrupt
Process ForkPoolWorker-1:
  File "/usr/lib/python3.6/multiprocessing/process.py", line 258, in _bootstrap
    self.run()
  File "/usr/lib/python3.6/multiprocessing/process.py", line 93, in run
    self._target(*self._args, **self._kwargs)
  File "/usr/lib/python3.6/multiprocessing/pool.py", line 108, in worker
    task = get()
  File "/usr/lib/python3.6/multiprocessing/queues.py", line 334, in get
    with self._rlock:
  File "/usr/lib/python3.6/multiprocessing/synchronize.py", line 95, in __enter__
    return self._semlock.__enter__()
KeyboardInterrupt
Traceback (most recent call last):
  File "/usr/lib/python3.6/multiprocessing/process.py", line 258, in _bootstrap
    self.run()
  File "/usr/lib/python3.6/multiprocessing/process.py", line 93, in run
    self._target(*self._args, **self._kwargs)
  File "/usr/lib/python3.6/multiprocessing/pool.py", line 108, in worker
    task = get()
  File "/usr/lib/python3.6/multiprocessing/queues.py", line 335, in get
    res = self._reader.recv_bytes()
  File "/usr/lib/python3.6/multiprocessing/connection.py", line 216, in recv_bytes
    buf = self._recv_bytes(maxlength)
  File "/usr/lib/python3.6/multiprocessing/connection.py", line 407, in _recv_bytes
    buf = self._recv(4)
  File "/usr/lib/python3.6/multiprocessing/connection.py", line 379, in _recv
    chunk = read(handle, remaining)
KeyboardInterrupt
Traceback (most recent call last):
  File "/usr/lib/python3.6/multiprocessing/process.py", line 258, in _bootstrap
    self.run()
  File "/usr/lib/python3.6/multiprocessing/process.py", line 93, in run
    self._target(*self._args, **self._kwargs)
  File "/usr/lib/python3.6/multiprocessing/pool.py", line 108, in worker
    task = get()
  File "/usr/lib/python3.6/multiprocessing/queues.py", line 334, in get
    with self._rlock:
  File "/usr/lib/python3.6/multiprocessing/synchronize.py", line 95, in __enter__
    return self._semlock.__enter__()
KeyboardInterrupt

I don't know how to fix this issue. Hope you guys can give a hint. Thank y'all so far!

EDIT The code of the script:

from datetime import date
from multiprocessing import Pool
from pdf2image import convert_from_path
from os import listdir, remove
from os.path import isfile, join, abspath, split, exists
import pytesseract
import sys
import os
import re
import tempfile

tmp_path = tempfile.gettempdir()  # replace with given output directory


def run(path):
    PDF_file = abspath(path)  # use absolute path of pdf file
    pages = convert_from_path(PDF_file, 500)
    page = pages[0]
    imgFile = abspath(join(tmp_path, "document"+str(date.today())+".jpg"))
    # save image to temp path
    page.save(imgFile, 'JPEG')
    # get text from image of page 1
    text = str(((pytesseract.image_to_string(Image.open(imgFile)))))
    if exists(imgFile):
        os.remove(imgFile)
    match = re.search(r"(Vertragsnummer\:\s)(\d+)\w+", text)
    if match == None:
        print("Could not find contract id")
        exit(1)
    else:
        f = split(PDF_file)
        d = join(tmp_path, match.group(2))
        if not exists(d):
            os.mkdir(d)
        PDF_file_new = join(d, f[1])
        print("New file: "+PDF_file_new)
        os.rename(PDF_file, PDF_file_new)


def run_in_dir(directory):
    files = [join(directory, f)
             for f in listdir(directory) if isfile(join(directory, f))]
    with Pool() as p:
        p.map_async(run, files)
        p.close()
        p.join()


if __name__ == "__main__":
    import argparse
    import cProfile
    parser = argparse.ArgumentParser(description="")
    parser.add_argument("-p", "--path", help="Path to specific PDF file.")
    parser.add_argument("-d", "--directory",
                        help="Path to folder containing PDF files.")
    args = parser.parse_args()
    # run(args.path)
    print(cProfile.run("run_in_dir(args.directory)"))

Answer 1

Try running the script without multiprocessing. In my case I found that

pytesseract.pytesseract.TesseractNotFoundError: tesseract is not installed or it's not in your path

Here's how to install it. I have no idea why the error message with multiprocessing is so unclear.

Also, remove exit(1) since it's intended for interactive shells not scripts.