Giving access to shared memory after child processes have already started

Question

How do I give child processes access to data in shared memory if the data is only available after the child processes have been spawned (using multiprocessing.Process)?

Answer 1

I think you are looking for mmap module

concerning the serializiation of data this question answer of course if you hope to avoid copy I have not the solution

EDIT

in fact you can use the non stdlib _mutliprocessing module in CPython 3.2 to have the address of the mmap object and use it with from_address of a ctypes object it is what in fact what does RawArray in fact of course you should not try to resize the mmap object as the address of mmap may change in this case

import mmap
import _multiprocessing
from ctypes import Structure,c_int

map = mmap.mmap(-1,4)
class A(Structure):
    _fields_ = [("x", c_int)]
x = _multiprocessing.address_of_buffer(map)
b=A.from_address(x[0])
b.x = 256

>>> map[0:4]
'\x00\x01\x00\x00'

to expose the memory after the child is created you have to map your memory with a real file that is calling

map = mmap.mmap(open("hello.txt", "r+b").fileno(),4)