问题描述
我需要从主进程中读取由 multiprocessing.Process 实例编写的字符串.我已经使用管理器和队列将参数传递给进程,所以使用管理器似乎很明显,但是Managers不支持字符串:
I need to read strings written by multiprocessing.Process instances from the main process. I already use Managers and queues to pass arguments to processes, so using the Managers seems obvious, but Managers do not support strings:
Manager() 返回的管理器将支持类型列表、字典、命名空间、锁、RLock、信号量、有界信号量、条件、事件、队列、值和数组.
A manager returned by Manager() will support types list, dict, Namespace, Lock, RLock, Semaphore, BoundedSemaphore, Condition, Event, Queue, Value and Array.
如何使用多处理模块中的管理器共享由字符串表示的状态?
How do I share state represented by a string using Managers from the multiprocessing module?
推荐答案
multiprocessing的Managers可以持有Values 又可以包含 c_char_p 来自 ctypes 模块:
multiprocessing's Managers can hold Values which in turn can hold instances of the type c_char_p from the ctypes module:
>>> import multiprocessing >>> import ctypes >>> v = multiprocessing.Value('c', "Hello, World!") Traceback (most recent call last): File "<stdin>", line 1, in <module> File "/usr/lib/python2.7/multiprocessing/__init__.py", line 253, in Value return Value(typecode_or_type, *args, **kwds) File "/usr/lib/python2.7/multiprocessing/sharedctypes.py", line 99, in Value obj = RawValue(typecode_or_type, *args) File "/usr/lib/python2.7/multiprocessing/sharedctypes.py", line 73, in RawValue obj.__init__(*args) TypeError: one character string expected >>> cstring = multiprocessing.Value(ctypes.c_char_p, "Hello, World!") >>> cstring <Synchronized wrapper for c_char_p(166841564)> >>> cstring.value 'Hello, World!'
对于 Python 3, 使用 c_wchar_p 代替 c_char_p
For Python 3, use c_wchar_p instead of c_char_p
另请参阅:发布我很难找到的原始解决方案.
因此,可以使用 Manager 在 Python 中的多个进程下共享字符串,如下所示:
So a Manager can be used to share a string beneath multiple processes in Python like this:
>>> from multiprocessing import Process, Manager, Value >>> from ctypes import c_char_p >>> >>> def greet(string): >>> string.value = string.value + ", World!" >>> >>> if __name__ == '__main__': >>> manager = Manager() >>> string = manager.Value(c_char_p, "Hello") >>> process = Process(target=greet, args=(string,)) >>> process.start() >>> process.join() >>> print string.value 'Hello, World!'