Python multiprocessing builtins.IOError: [Errno 22] Invalid argument

Question

Not sure why this error is appearing. I've searched around to no avail. I decided to take a punt at making my script run multi-threaded using the multiprocessing module, and if I remove that code the script runs fine.

So I ran the debugger and it also doesn't encounter any error with the multi-threading code, which seems a bit weird. But when I try to run the script just normally, it prints under 3.2.3:

Python 3.2.3 (default, Apr 11 2012, 07:12:16) [MSC v.1500 64 bit (AMD64)]
Type "help", "copyright", "credits" or "license" for more information.
[evaluate scratch.py]
Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "C:\Python32\Lib\multiprocessing\forking.py", line 369, in main
    self = load(from_parent)
AttributeError: 'module' object has no attribute 'search_letters_in_words'
Traceback (most recent call last):
  File "C:\Program Files (x86)\Wing IDE 4.1\src\debug\tserver\_sandbox.py", line 122, in <module>
  File "C:\Python32\Lib\multiprocessing\process.py", line 132, in start
    self._popen = Popen(self)
  File "C:\Python32\Lib\multiprocessing\forking.py", line 269, in __init__
    to_child.close()
builtins.IOError: [Errno 22] Invalid argument

Edit: I switched over to 3.3 to see what happens and it unconsistently consistently throws one of these two tracebacks:

Python 3.3.0 (v3.3.0:bd8afb90ebf2, Sep 29 2012, 10:57:17) [MSC v.1600 64 bit (AMD64)]
Type "help", "copyright", "credits" or "license" for more information.
[evaluate scratch.py]
Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "C:\Python33\Lib\multiprocessing\forking.py", line 344, in main
    self = load(from_parent)
AttributeError: 'module' object has no attribute 'search_letters_in_words'
Traceback (most recent call last):
  File "C:\Program Files (x86)\Wing IDE 4.1\src\debug\tserver\_sandbox.py", line 122, in <module>
  File "C:\Python33\Lib\multiprocessing\process.py", line 111, in start
    self._popen = Popen(self)
  File "C:\Python33\Lib\multiprocessing\forking.py", line 243, in __init__
    dump(process_obj, to_child, HIGHEST_PROTOCOL)
  File "C:\Python33\Lib\multiprocessing\forking.py", line 160, in dump
    ForkingPickler(file, protocol).dump(obj)
builtins.BrokenPipeError: [Errno 32] Broken pipe

Python 3.3.0 (v3.3.0:bd8afb90ebf2, Sep 29 2012, 10:57:17) [MSC v.1600 64 bit (AMD64)]
Type "help", "copyright", "credits" or "license" for more information.
[evaluate scratch.py]
Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "C:\Python33\Lib\multiprocessing\forking.py", line 344, in main
    self = load(from_parent)
AttributeError: 'module' object has no attribute 'search_letters_in_words'

Edit #2 Added traceback when calling from the commandline:

D:\Python\PythonRepo>scratch.py > d:\download\error.txt
Traceback (most recent call last):
  File "D:\Python\PythonRepo\scratch.py", line 122, in <module>
    thread.start()
  File "C:\Python32\Lib\multiprocessing\process.py", line 131, in start
    from .forking import Popen
  File "C:\Python32\Lib\multiprocessing\forking.py", line 180, in <module>
    import _subprocess
ImportError: No module named '_subprocess'

Here's the multiprocessing code I've written so far. It could be (hah who am I kidding, probably is!)buggy but I'm not sure what's wrong as it looks correct (doesn't it always?).

wordList = pickle.load( open( r'd:\download\allwords.pickle', 'rb')) #a list
combos = make_letter_combinations(3) # a list
split = split_list_multi(combos) #2 item tuple with a dict and a number
if __name__ == '__main__':
    multiprocessing.freeze_support()
    jobs = []
    for num in range(split[1]):
        listLetters = split[0][str(num)] #a list
        thread = multiprocessing.Process(target=search_letters_in_words, args=(listLetters,wordList))
        jobs.append(thread)
        thread.start()
    for j in jobs:
        j.join()

Edit: Here's the search_letters_in_words_ function:

def search_letters_in_words(listOfLetters,wordlist):
    results = {}
    for letters in listOfLetters:
        results[letters] = [i for i in wordlist if letters in i]
    return results

If anyone could point out what I'm doing wrong I'd appreciate it!

Answer 1

Try running the script from the command-line, not through Wing IDE:

python scripy.py