Tqdm + pool.imap_unordered

demo.py

from tqdm import tqdm
from multiprocessing import Pool

def myfn(x):
  return x ** 2


with Pool() as pool:
  args = list(range(1_000_000))
  work = pool.imap_unordered(myfn, args, chunksize=100)
  results = []
  for out in tqdm(work, total=len(args)):
    results.append(out)