Example of how to use a anonymous mmap block with the multiprocessing module

mmap-mp.py

from multiprocessing import Pool
import mmap

mm = mmap.mmap(-1, 12, flags=mmap.MAP_SHARED|mmap.MAP_ANONYMOUS)
n = mm.write(b"lots of data")
mm.seek(0)

print(mm.read().decode('ascii'))
mm.seek(0)

def f(x):
    offset, char = x
    mm[offset:offset+1] = str(char).encode('ascii')

with Pool(3) as p:
    p.map(f, [(0, "f"), (1, "o"), (2, "o")])

print(mm.read().decode('ascii'))

The mmap could also be file backed if persistence was required (remove MAP_ANONYMOUS and pass a fileno).

Oh! Very nice! I guess that article was wrong. I'd much rather use mmap than the shared_memory module. Thanks!