問題描述

我正在 Python 中嘗試多處理，并嘗試在兩個(gè)進(jìn)程之間共享一個(gè)字符串?dāng)?shù)組.這是我的python代碼:

I am experimenting multiprocessing in Python and tried to share an Array of strings among two processes. Here is my python code :

from multiprocessing import Process, Array, Value
import ctypes

def f1(a, v):
    for i, l in enumerate(['a', 'b', 'c']):
        a[i] = l*3

    v.value += 1

    print "f1 : ", a[:], v.value

def f2(a,v):

    v.value += 1

    print "f2 : ", a[:], v.value

if __name__ == '__main__':
    val = Value(ctypes.c_int, 0)
    arr = Array(ctypes.c_char_p, 3)

    print "Before :", arr[:], val.value

    p = Process(target=f1, args=(arr, val))
    p2 = Process(target=f2, args=(arr, val))

    p.start()
    p2.start()

    p.join()
    p2.join()

    print "After : ", arr[:], val.value

當(dāng)我運(yùn)行腳本時(shí)，我看到 arr 已正確填充并在 f1() 中可用，但在 f2() 中不可用.結(jié)果如下:

When I run the script I see that arr is correctly populated and available in f1() but not in f2(). Here is the result:

    % python /tmp/tests.py
    Before : [None, None, None] 0
    f1 :  ['aaa', 'bbb', 'ccc'] 1
    f2 :  ['x01', 'x11', 'x01'] 2
    After :  ['x01', 'x01', 'x01'] 2

我是否忽略了什么?

提前感謝您的反饋.:)

Thanks in advance for your feedback. :)

推薦答案

我的猜測(cè)是:

arr 存儲(chǔ) 3 個(gè)指針.f1() 將它們分配給沒有意思是在當(dāng)前流程之外.f2() 嘗試訪問此時(shí)包含垃圾的無意義地址.

arr stores 3 pointers. f1() assigns them to memory addresses that have no meaning outside current process. f2() tries to access the meaningless addresses that contain junk at this point.

分配給在所有過程中都有意義的值似乎有幫助:

Assigning to values that have meaning in all processes seems to help:

from __future__ import print_function
import ctypes
import time
from multiprocessing import Process, Array, Value

values = [(s*4).encode('ascii') for s in 'abc']

def f1(a, v):
    for i, s in enumerate(values):
        a[i] = s

    v.value += 1

    print("f1 : ", a[:], v.value)

def f2(a,v):
    v.value += 1
    print("f2 : ", a[:], v.value)

def main():
    val = Value(ctypes.c_int, 0)
    arr = Array(ctypes.c_char_p, 3)

    print("Before :", arr[:], val.value)

    p = Process(target=f1, args=(arr, val))
    p2 = Process(target=f2, args=(arr, val))

    p.start()
    p2.start()

    p.join()
    p2.join()

    print("After : ", arr[:], val.value)

if __name__ == '__main__':
    main()

輸出

Before : [None, None, None] 0
f1 :  ['aaaa', 'bbbb', 'cccc'] 1
f2 :  ['aaaa', 'bbbb', 'cccc'] 2
After :  ['aaaa', 'bbbb', 'cccc'] 2

這篇關(guān)于共享數(shù)組在 python 多處理中未正確共享的文章就介紹到這了，希望我們推薦的答案對(duì)大家有所幫助，也希望大家多多支持html5模板網(wǎng)！