线程池

import time
from concurrent.futures import ThreadPoolExecutor
def func(i):
    time.sleep(2)
    print(i)
    return i**2
tpool = ThreadPoolExecutor(max_workers = 5)
t_lst = []
for i in range(10):
    t = tpool.submit(func,i)
    t_lst.append(t)
tpool.shutdown()
print("主线程")
for t in t_lst:
    print("***",t.result())