import time
import threading
from subprocess import check_output
from queue import Queue

NUM_THREADS = 10
NUM_JOBS = 20

# lock to single-thread printing
print_lock = threading.Lock()

# Create the queue and threader
q = Queue()

def exampleJob(worker):
    """Run the external program, get output and strip leading/trailing whitespace"""

    # the external program "job.sh" just waits 1 second and echos input parameters
    # we must convert the "bytes" output to a string and remove trailing '\n'
    result = check_output(['./job.sh', 'hello', 'world']).decode("utf-8").strip()

    # print the result of the job
#    with print_lock:
#        print(threading.current_thread().name, worker, result)
    # printing without locking seems OK (on MacOS, anyway)
    print(threading.current_thread().name, worker, result)

def threader():
    """Gets a job from the queue and processes it."""

    while True:
        worker = q.get()
        exampleJob(worker)
        q.task_done()

# Start a fixed number of threads
for x in range(NUM_THREADS):
    t = threading.Thread(target=threader)
    t.daemon = True
    t.start()

start = time.time()

# generate a number of jobs and put them on the queue
# the job is just the "job number"
for worker in range(NUM_JOBS):
    q.put(worker)
q.join()

# print total elapsed time
delta = time.time() - start
print(f'Took {delta:.2f}s')