fils.py

#!/usr/bin/env python3
from concurrent.futures import ThreadPoolExecutor, as_completed
from itertools import zip_longest

def grouper(iterable, n=1000, fillvalue=None):
    args = [iter(iterable)] * n
    return zip_longest(*args, fillvalue=fillvalue)

def async_func(number):
    return number * number

my_list = [1, 2, 3]

with ThreadPoolExecutor(max_workers=8) as executor:
    for chunk in grouper(my_list):
        futures = {}
        for number in chunk:
            if not number: continue # skip
            futures[executor.submit(async_func, number)] = number
        
        for future in as_completed(futures):
            number = futures[future]
            
            try:
                result = future.result()
                print(f'{number}: {result}')
            except Exception as e:
                print(e)