Multithreading using Python

threading.py

#!/usr/bin/env python3

import concurrent.futures as futures
import random
import threading
from concurrent.futures.thread import ThreadPoolExecutor

l = [[1, 2, 3], [2, 3, 4], [3, 5, 7], [3, 5, 8], [3, 5, 9]]

def foo(bar):
    val = threading.get_native_id() * random.randint(1, 100)
    print("hello {} {}".format(val, bar))
    return val, bar


def task2(thread, list):
    print(f"You are inside {thread} ")
    for i in list:
        print(i)
    return thread


def task3(thread):
    print(f"Got {thread}")


if __name__ == "__main__":
    with futures.thread.ThreadPoolExecutor(5) as executor:
        futures1 = [executor.submit(foo, sub_list) for sub_list in l]
        futures2 = list()
        futures3 = list()
        for future1 in futures.as_completed(futures1):
            # get the result
            thread_no, list_values = future1.result()
            # check if we should trigger a follow-up task
            future2 = executor.submit(task2, thread_no, list_values)
            futures2.append(future2)
        for future2 in futures.as_completed(futures2):
            thread_no_2 = future2.result()
            future3 = executor.submit(task3, thread_no_2)
            futures3.append(future3)