子进程不需要close()吗？

用户7296618635

#1 Created at ... [Delete] [Delete and Lock User]

例程里只有用到了join()，没有close()。这个close()函数什么时候使用？

from multiprocessing import Process
import os

# 子进程要执行的代码
def run_proc(name):
    print('Run child process %s (%s)...' % (name, os.getpid()))

if __name__=='__main__':
    print('Parent process %s.' % os.getpid())
    p = Process(target=run_proc, args=('test',))
    print('Child process will start.')
    p.start()
    p.join()
    print('Child process end.')

我所有的向往呀

#2 Created at ... [Delete] [Delete and Lock User]

我也是纳闷为啥不加close(), 然后我自个在join()前面加了close(), 结果 = =

Traceback (most recent call last):
  File "/Volumes/AppData/Code/Python/process_thread.py", line 135, in <module>
    pw.close()
  File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/multiprocessing/process.py", line 181, in close
    raise ValueError("Cannot close a process while it is still running. "
ValueError: Cannot close a process while it is still running. You should first call join() or terminate().

Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/multiprocessing/spawn.py", line 116, in spawn_main
    exitcode = _main(fd, parent_sentinel)
  File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/multiprocessing/spawn.py", line 126, in _main
    self = reduction.pickle.load(from_parent)
  File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/multiprocessing/synchronize.py", line 110, in __setstate__
    self._semlock = _multiprocessing.SemLock._rebuild(*state)
FileNotFoundError: [Errno 2] No such file or directory
Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/multiprocessing/spawn.py", line 116, in spawn_main
    exitcode = _main(fd, parent_sentinel)
  File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/multiprocessing/spawn.py", line 126, in _main
    self = reduction.pickle.load(from_parent)
  File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/multiprocessing/synchronize.py", line 110, in __setstate__
    self._semlock = _multiprocessing.SemLock._rebuild(*state)
FileNotFoundError: [Errno 2] No such file or directory

我猜测应该是Queue模块的原因, 因为

pw / pr 来自于 q

而 q 来自于 Queue