tqdm update with apply_async in multiprocessing code example

Example: tqdm update with apply_async in multiprocessing

import time
import random
from multiprocessing import Pool
from tqdm import tqdm

def myfunc(a):
    time.sleep(random.random())
    return a ** 2

pool = Pool(2)
'''
for _ in tqdm(pool.imap_unordered(myfunc, range(100)), total=100):
    pass
'''
pbar = tqdm(total=100)
def update(*a):
    pbar.update()
    # tqdm.write(str(a))
for i in range(pbar.total):
    pool.apply_async(myfunc, args=(i,), callback=update)
# tqdm.write('scheduled')
pool.close()
pool.join()