問題描述
我需要從主進程中讀取由 multiprocessing.Process 實例編寫的字符串.我已經使用管理器和隊列將參數傳遞給進程，所以使用管理器似乎很明顯，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() 返回的管理器將支持類型列表、字典、命名空間、鎖、RLock、信號量、有界信號量、條件、事件、隊列、值和數組.
A manager returned by Manager() will support types list, dict, Namespace, Lock, RLock, Semaphore, BoundedSemaphore, Condition, Event, Queue, Value and Array.
如何使用多處理模塊中的管理器共享由字符串表示的狀態?
How do I share state represented by a string using Managers from the multiprocessing module?
推薦答案
multiprocessing的Managers可以持有Values 又可以包含 c_char_p 來自 ctypes 模塊:
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!'
對于 Python 3， 使用 c_wchar_p 代替 c_char_p
For Python 3, use c_wchar_p instead of c_char_p
另請參閱:發布我很難找到的原始解決方案.
因此，可以使用 Manager 在 Python 中的多個進程下共享字符串，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!'
這篇關于如何在 Python 中使用 Managers() 在多個進程之間共享字符串?的文章就介紹到這了，希望我們推薦的答案對大家有所幫助，也希望大家多多支持html5模板網！