from multiprocessing import Pool


def write_file(file: str):
    f = open(file, 'w')
    for item in range(0, 1500000):
        f.write("%sn" % item)
    f.close()


if __name__ == '__main__':
    list_files = ['1.txt', '2.txt', '3.txt']
    with Pool(3) as p:
        p.map(write_file, list_files)

from multiprocessing import Process
import time
pdict = {}
for fname in list_files:
    p = Process(target = write_file, args = (fname,))
    pdict[fname] = p
    p.start()
while pdict:
    time.sleep(10)
    for pname in pdict:
        if pdict[pname].exitcode == None or pdict[pname].is_alive():
            pdict[pname].terminate() #killing old; that should also free file resource
            pdict[pname] = Process(target = write_file, args = (pname,))
            pdict[pname].start() #simply creating new and starting
        else:
            del pdict[pname]