python 多进程共享数据的读与写

1. 父进程向子进程传参

1.1python通常的数据结构可以传给子进程读，但子进程写无效：

from multiprocessing import Pool, Manager

def chid_proc(test_dict, i):
    print '{} process, before modify: {}'.format(i, test_dict)
    test_dict[i] = i * i
    print '{} process, after modify: {}'.format(i, test_dict)


if __name__ == '__main__':
    td = {'a':1}
    pool = Pool(3)
    for i in xrange(0, 3):
        pool.apply_async(chid_proc, args=(td, i))
    pool.close()
    pool.join()
    print 'after pool:  {}'.format(td)

结果：

0 process, before modify: {'a': 1}
0 process, after modify: {'a': 1, 0: 0}
1 process, before modify: {'a': 1}
2 process, before modify: {'a': 1}
1 process, after modify: {'a': 1, 1: 1}
2 process, after modify: {'a': 1, 2: 4}
after pool:  {'a': 1}

1.2 使用Manager.dict实现进程间共享数据的修改

from multiprocessing import Pool, Manager

def chid_proc(test_dict, i):
    print '{} process, before modify: {}'.format(i, test_dict)
    test_dict[i] = i * i
    print '{} process, after modify: {}'.format(i, test_dict)



if __name__ == '__main__':
    #td = {'a':1}
    td = Manager().dict()
    td['a'] = 1
    pool = Pool(3)
    for i in xrange(0, 3):
        pool.apply_async(chid_proc, args=(td, i))
    pool.close()
    pool.join()
    print 'after pool:  {}'.format(td)

结果：

0 process, before modify: {'a': 1}
0 process, after  modify: {'a': 1, 0: 0}
1 process, before modify: {'a': 1, 0: 0}
1 process, after  modify: {'a': 1, 0: 0, 1: 1}
2 process, before modify: {'a': 1, 0: 0, 1: 1}
2 process, after  modify: {'a': 1, 0: 0, 2: 4, 1: 1}
after pool:  {'a': 1, 0: 0, 2: 4, 1: 1}