#!/usr/bin/env python3

from concurrent import futures
from time import sleep


def count(name, target):
    """ Counts from 1 to target integer """
    for i in range(1, target + 1):
        sleep(1)
    return print(name + " - Success")


with futures.ThreadPoolExecutor(max_workers=20) as executor:
    count_jobs = [3, 4, 1, "abc", 7, 2, 6, 5]
    # Builds a dictionary, key=(futures object) value=(item from list)
    threads = {executor.submit(count, "count_for_{}".format(str(job)), job): job for job in count_jobs}
    for future in futures.as_completed(threads):
        try:
            future.result()
        except Exception as err:
            print("!!! ERROR {}: {} !!!".format("count_for_{}".format(threads[future]), err))
            # Comment this to ignore errors
            raise