How do I pass large numpy arrays between python subprocesses without saving to disk?

Question

Is there a good way to pass a large chunk of data between two python subprocesses without using the disk? Here\'s a cartoon example of what I\'m hoping to accomplish:

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Answer 1

While googling around for more information about the code Joe Kington posted, I found the numpy-sharedmem package. Judging from this numpy/multiprocessing tutorial it seems to share the same intellectual heritage (maybe largely the same authors? -- I'm not sure).

Using the sharedmem module, you can create a shared-memory numpy array (awesome!), and use it with multiprocessing like this:

import sharedmem as shm
import numpy as np
import multiprocessing as mp

def worker(q,arr):
    done = False
    while not done:
        cmd = q.get()
        if cmd == 'done':
            done = True
        elif cmd == 'data':
            ##Fake data. In real life, get data from hardware.
            rnd=np.random.randint(100)
            print('rnd={0}'.format(rnd))
            arr[:]=rnd
        q.task_done()

if __name__=='__main__':
    N=10
    arr=shm.zeros(N,dtype=np.uint8)
    q=mp.JoinableQueue()    
    proc = mp.Process(target=worker, args=[q,arr])
    proc.daemon=True
    proc.start()

    for i in range(3):
        q.put('data')
        # Wait for the computation to finish
        q.join()   
        print arr.shape
        print(arr)
    q.put('done')
    proc.join()

Running yields

rnd=53
(10,)
[53 53 53 53 53 53 53 53 53 53]
rnd=15
(10,)
[15 15 15 15 15 15 15 15 15 15]
rnd=87
(10,)
[87 87 87 87 87 87 87 87 87 87]