Closed as not planned
Description
Bug report
Bug description:
The following code runs successfully in 3.13.1 (and earlier versions) but fails in 3.14.0a3+ (5a584c8):
from __future__ import annotations
from unittest import TestCase
from multiprocessing import Manager, Pool
LETTERS: dict[str, int]
def add_letter(letter: str) -> None:
LETTERS[letter] += 1
class TestAsdf(TestCase):
def setUp(self):
global LETTERS
LETTERS = Manager().dict(
a = 0,
s = 0,
d = 0,
f = 0,
)
def test_asdf(self):
with Pool() as pool:
pool.map(
add_letter,
list('asdf'))
print(LETTERS)Run successfully, it produces this output:
$ python3.11 -m unittest asdf
{'a': 1, 's': 1, 'd': 1, 'f': 1}
In 3.14, it fails with NameError:
$ python3.14 -m unittest asdf
======================================================================
ERROR: test_asdf (asdf.TestAsdf.test_asdf)
----------------------------------------------------------------------
multiprocessing.pool.RemoteTraceback:
"""
Traceback (most recent call last):
File "/usr/local/lib/python3.14/multiprocessing/pool.py", line 125, in worker
result = (True, func(*args, **kwds))
~~~~^^^^^^^^^^^^^^^
File "/usr/local/lib/python3.14/multiprocessing/pool.py", line 48, in mapstar
return list(map(*args))
File "/home/nick/asdf.py", line 9, in add_letter
LETTERS[letter] += 1
^^^^^^^
NameError: name 'LETTERS' is not defined
"""
The above exception was the direct cause of the following exception:
Traceback (most recent call last):
File "/home/nick/asdf.py", line 24, in test_asdf
pool.map(
~~~~~~~~^
add_letter,
^^^^^^^^^^^
list('asdf'))
^^^^^^^^^^^^^
File "/usr/local/lib/python3.14/multiprocessing/pool.py", line 367, in map
return self._map_async(func, iterable, mapstar, chunksize).get()
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^
File "/usr/local/lib/python3.14/multiprocessing/pool.py", line 774, in get
raise self._value
NameError: name 'LETTERS' is not definedThis example looks stupid, but it is based on real-world test code.
CPython versions tested on:
3.11, 3.13, 3.14, CPython main branch
Operating systems tested on:
Linux