Python 3.4 中的多处理是否损坏？

Question

我正在尝试使用 Python 3 中的多处理模块。但是，每次我尝试设置池时，都会得到以下回溯。

Traceback (most recent call last):
  File "testmp.py", line 7, in <module>
    with Pool(5) as p:
  File "/usr/lib/python3.4/multiprocessing/context.py", line 118, in Pool
    context=self.get_context())
  File "/usr/lib/python3.4/multiprocessing/pool.py", line 150, in __init__
    self._setup_queues()
  File "/usr/lib/python3.4/multiprocessing/pool.py", line 243, in _setup_queues
    self._inqueue = self._ctx.SimpleQueue()
  File "/usr/lib/python3.4/multiprocessing/context.py", line 110, in SimpleQueue
    from .queues import SimpleQueue
  File "/usr/lib/python3.4/multiprocessing/queues.py", line 20, in <module>
    from queue import Empty, Full
ImportError: cannot import name 'Empty'

可以轻松触发的最简单代码是多处理模块文档中的第一个示例。

from multiprocessing import Pool

def f(x):
    return x*x

if __name__ == '__main__':
    with Pool(5) as p:
        print(p.map(f, [1, 2, 3]))

（来源：https://docs.python.org/3.4/library/multiprocessing.html）

我的问题：这是 Python 3.4 中的错误吗？还是我做错了什么？等效代码适用于 Python 2.7.

Answer 1

您有一个名为 queue 的 local 模块；它会干扰 standard library module.

删除它或重命名它，您的代码将再次运行：

Whosebug-3.4 mj$ cat test.py 
from multiprocessing import Pool

def f(x):
    return x*x

if __name__ == '__main__':
    with Pool(5) as p:
        print(p.map(f, [1, 2, 3]))

Whosebug-3.4 mj$ touch queue.py
Whosebug-3.4 mj$ bin/python test.py 
Traceback (most recent call last):
  File "test.py", line 7, in <module>
    with Pool(5) as p:
  File "/.../python3.4/multiprocessing/context.py", line 118, in Pool
    context=self.get_context())
  File "/.../python3.4/multiprocessing/pool.py", line 150, in __init__
    self._setup_queues()
  File "/.../python3.4/multiprocessing/pool.py", line 243, in _setup_queues
    self._inqueue = self._ctx.SimpleQueue()
  File "/.../lib/python3.4/multiprocessing/context.py", line 110, in SimpleQueue
    from .queues import SimpleQueue
  File "/.../lib/python3.4/multiprocessing/queues.py", line 20, in <module>
    from queue import Empty, Full
ImportError: cannot import name 'Empty'
Whosebug-3.4 mj$ rm queue.py
Whosebug-3.4 mj$ bin/python test.py 
[1, 4, 9]

如果您找不到它，运行 python3 -c 'import queue; print(queue.__file__)'。

Python 3.4 中的多处理是否损坏？

Is multiprocessing in Python 3.4 broken?

python

multiprocessing

importerror

python-3.x

python-3.4