Does process in python have its own os.environ copy?

Question

I'm wondering, does process in python have its own copy of os.environ ? Ie is it safe to set os.environ from the process, and is it guaranteed that it will not be overwritten from another process?

import os
import time
import random
from multiprocessing import Process


def f1(i):
    time.sleep(random.randint(0,3))

    os.environ["CUDA_DEVICE_ORDER"] = "PCI_BUS_ID"
    os.environ['CUDA_VISIBLE_DEVICES'] = str(i)
    print('i:', i)

    time.sleep(random.randint(0, 3))

    print('i:', i, "os.environ['CUDA_VISIBLE_DEVICES']", os.environ['CUDA_VISIBLE_DEVICES'])



def run_me():
    n = 3
    process_list = []
    for i in range(n):
        p = Process(target=f1, args=(i,))
        p.start()
        process_list.append(p)

    for p in process_list:
        p.join()


if __name__ == "__main__":
    run_me()

Example of output:

i: 2
i: 0
i: 0 os.environ['CUDA_VISIBLE_DEVICES'] 0
i: 2 os.environ['CUDA_VISIBLE_DEVICES'] 2
i: 1
i: 1 os.environ['CUDA_VISIBLE_DEVICES'] 1

Answer 1

No process is allowed to modify the enviornment variables of another process, and every process is given its own fresh copy of enviorment variables. It will initally contain a copy of the parent process' env vars unless otherwise specified.