問題描述

我想使用 multiprocessing.Value 在多個進程中使用變量，但 Python 文檔中的語法并不清楚.誰能告訴我應該使用什么類型(我的變量是一個字母)，以及將變量名放在哪里?

I want to use?multiprocessing.Value?to use a variable in multiple processes, but the syntax is not clear on Python's documentation. Can anyone tell me what should I use as type (my variable is a letter), and where to put my variable's name ?

編輯

我嘗試使用管理器在進程之間共享我的信件.但我現在唯一擁有的是在 Python Shell 中打印的 Value('ctypes.c_char_p', '(The key you hit here)') 仍然沒有聲音.使用管理器時，控制臺似乎也比平時慢了一點.在我按下鍵和 Value 出現在屏幕上之間，有將近一秒的延遲.

I tried using the?Manager?to share my letter between processes. But the only thing I have now is Value('ctypes.c_char_p', '(The key you hit here)')?printed in the Python Shell and still no sound. The console also seems a bit slower than usual when using the manager. There's an almost one second delay between the time I hit the key and when the Value appears on screen.

我的代碼現在看起來像這樣:

My code now looks like this :

#Import 
from tkinter import * 
import wave 
import winsound 
import multiprocessing 

#Functions 

def key(event):

     temp = event.char
     manager = multiprocessing.Manager()
     manager.Value(ctypes.c_char_p, temp)
     hitkey = manager.Value(ctypes.c_char_p, temp)
     instance = multiprocessing.Process(target=player, args=(hitkey,)) 
     instance.start()



def player(hitkey):
     print(hitkey + "1")
     winsound.PlaySound(hitkey + '.wav', winsound.SND_FILENAME|winsound.SND_NOWAIT|winsound.SND_ASYNC) 


if __name__ == "__main__":



     #Initialisation 
     fenetre = Tk() 
     frame = Frame(fenetre, width=200, height=100)
     #TK

     frame.focus_set()
     frame.bind("<Key>", key)
     frame.pack()
     fenetre.mainloop()

推薦答案

multiprocessing.Value，它只是一個和其他類一樣的類.Value 構造函數的簽名 描述得非常完美:

multiprocessing.Value(typecode_or_type, *args[, lock])

返回一個從共享內存分配的 ctypes 對象.默認情況下，返回值實際上是對象的同步包裝器.

Return a ctypes object allocated from shared memory. By default the return value is actually a synchronized wrapper for the object.

typecode_or_type 確定返回對象的類型:它是 ctypes 類型或所用類型的單字符類型代碼由 array 模塊.*args 被傳遞給構造函數輸入.

typecode_or_type determines the type of the returned object: it is either a ctypes type or a one character typecode of the kind used by the array module. *args is passed on to the constructor for the type.

如果 lock 為 True(默認值)，則創建一個新的鎖對象以同步對值的訪問.如果 lock 是 Lock 或RLock 對象然后將用于同步訪問價值.如果 lock 是 False 則訪問返回的對象將不會被鎖自動保護，所以不一定過程安全".

If lock is True (the default) then a new lock object is created to synchronize access to the value. If lock is a Lock or RLock object then that will be used to synchronize access to the value. If lock is False then access to the returned object will not be automatically protected by a lock, so it will not necessarily be "process-safe".

您甚至還有一些使用示例之后.特別是 typecode_or_type 可以是 array 模塊(例如 'i' 用于有符號整數，'f' 用于浮點等)或ctypes 類型，如 ctypes.c_int 等.

You even have some examples of its use afterwards. In particolar the typecode_or_type can be one of the typecodes that are listed in the documentation for the array module(e.g. 'i' for signed integer, 'f' for float etc.) or a ctypes type, like ctypes.c_int etc.

如果你想要一個包含單個字母的 Value，你可以這樣做:

If you want to have a Value containing a single letter you can do:

>>> import multiprocessing as mp
>>> letter = mp.Value('c', 'A')
>>> letter
<Synchronized wrapper for c_char('A')>
>>> letter.value
'A'

更新

您的代碼的問題是類型代碼 'c' 表示字符 not 字符串.如果你想保存一個字符串，你可以使用類型 ctypes.c_char_p:

The problem with your code is that the typecode 'c' means character not string. If you want to hold a string you can use the type ctypes.c_char_p:

>>> import multiprocessing as mp
>>> import ctypes
>>> v = mp.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
>>> v = mp.Value(ctypes.c_char_p, "Hello, World!")
>>> v
<Synchronized wrapper for c_char_p(166841564)>
>>> v.value
'Hello, World!'

對于 Python 3，使用 c_wchar_p 代替 c_char_p

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