Python多进程报错AttributeError: Can‘t pickle local object ‘run_pool.＜locals＞.run‘

原代码

import multiprocessing
import time
from multiprocessing import Pool

def run_pool():
    def run(k):
        print(k, multiprocessing.current_process().name)
        time.sleep(1)

    def pool():
        p = Pool(8)
        p.map(run, range(16))
        p.close()
        p.join()
    pool()

if __name__ == '__main__':
    t0 = time.time()
    run_pool()
    t1 = time.time()
    print(t1 - t0)
"""
报错信息：
Traceback (most recent call last):
  File "C:/Project/auto_label_english/pool.py", line 19, in 
    run_pool()
  File "C:/Project/auto_label_english/pool.py", line 15, in run_pool
    pool()
  File "C:/Project/auto_label_english/pool.py", line 12, in pool
    p.map(run, range(16))
  File "C:\Users\E14\Anaconda3\envs\auto_label_english\lib\multiprocessing\pool.py", line 266, in map
    return self._map_async(func, iterable, mapstar, chunksize).get()
  File "C:\Users\E14\Anaconda3\envs\auto_label_english\lib\multiprocessing\pool.py", line 644, in get
    raise self._value
  File "C:\Users\E14\Anaconda3\envs\auto_label_english\lib\multiprocessing\pool.py", line 424, in _handle_tasks
    put(task)
  File "C:\Users\E14\Anaconda3\envs\auto_label_english\lib\multiprocessing\connection.py", line 206, in send
    self._send_bytes(_ForkingPickler.dumps(obj))
  File "C:\Users\E14\Anaconda3\envs\auto_label_english\lib\multiprocessing\reduction.py", line 51, in dumps
    cls(buf, protocol).dump(obj)
AttributeError: Can't pickle local object 'run_pool..run'
"""

报错原因

子进程能识别的符号是跟主进程一样的，我的执行函数是局部函数，进程无法识别。应该改成全局函数，或者类里面的静态方法。

修改后的代码

import multiprocessing
import time
from multiprocessing import Pool

def run(k):
    print(k, multiprocessing.current_process().name)
    time.sleep(1)

def run_pool():
    def pool():
        p = Pool(8)
        p.map(run, range(16))
        p.close()
        p.join()
    pool()

if __name__ == '__main__':
    t0 = time.time()
    run_pool()
    t1 = time.time()
    print(t1 - t0)
    
"""
结果输出：
0 SpawnPoolWorker-1
1 SpawnPoolWorker-3
2 SpawnPoolWorker-2
3 SpawnPoolWorker-5
4 SpawnPoolWorker-4
5 SpawnPoolWorker-6
6 SpawnPoolWorker-7
7 SpawnPoolWorker-8
8 SpawnPoolWorker-1
9 SpawnPoolWorker-2
10 SpawnPoolWorker-3
11 SpawnPoolWorker-6
12 SpawnPoolWorker-7
13 SpawnPoolWorker-4
14 SpawnPoolWorker-5
15 SpawnPoolWorker-8
2.453700542449951
"""