[hot_gril]

I tried this on a Linux machine in Py3 earlier, which I think is equivalent to your example:

  from multiprocessing import Pool

  shared = {}

  def f(x):
    global shared  # idk if this matters but tried without it too
    shared[x] = x
    print(shared)

  if __name__ == '__main__':
    with Pool(5) as p:
      p.map(f, [1, 2, 3])
    print(shared)

It printed {1: 1}, {2: 2}, {3: 3} then {} at the end. So the parent and other children didn't see the change made by each child. Doesn't seem like they're RW sharing.

[Galanwe]

Yes, as mentioned, the workers get a copy of the interpreter states. Every modification made in a worker to these objects stay local to the worker. These tricks are for sending data to a worker, not receiving back data.