How to distribute work to a set of worker threads in Python?

To distribute work among a bunch of worker threads, use the concurrent.futures module, specifically ThreadPoolExecutor class.

With this alternative, you can manually write your own logic if you want fine control over the scheduling algorithm. Use the queue module to create a queue containing a list of jobs. The Queue class maintains a list of objects and has a .put(obj) method that adds items to the queue and a .get() method that returns an item. This class will take care of the necessary locking to ensure that each job is only distributed once.

Example

The following is an example -

import threading, queue, time

# The worker thread gets jobs off the queue. When the queue is empty, it
# assumes there will be no more work and exits.
def worker():
   print('Running worker')
   time.sleep(0.1)
   while True:
      try:
         arg = q.get(block=False)
      except queue.Empty:
         print('Worker', threading.current_thread(), end=' ')
         print('queue empty')
         break
      else:
         print('Worker', threading.current_thread(), end=' ')
         print('running with argument', arg)
         time.sleep(0.5)

# Create a queue
q = queue.Queue()

# Start a pool of 5 workers
for i in range(5):
   t = threading.Thread(target=worker, name='worker %i' % (i+1))
   t.start()

# Begin adding work to the queue
for i in range(50):
   q.put(i)

# Give threads time to run
print('Main thread sleeping')
time.sleep(5)

Output

Running worker
Running worker
Running worker
Running worker
Running worker
Main thread sleeping
Worker  running with argument 0
Worker  running with argument 1
Worker  running with argument 2
Worker  running with argument 3
Worker  running with argument 4
Worker  running with argument 5
Worker  running with argument 6
Worker  running with argument 7
Worker  running with argument 8
Worker  running with argument 9
Worker  running with argument 10
Worker  running with argument 11
Worker  running with argument 12
Worker  running with argument 13
Worker  running with argument 14
Worker  running with argument 15
Worker  running with argument 16
Worker  running with argument 17
Worker  running with argument 18
Worker  running with argument 19
Worker  running with argument 20
Worker  running with argument 21
Worker  running with argument 22
Worker  running with argument 23
Worker  running with argument 24
Worker  running with argument 25
Worker  running with argument 26
Worker  running with argument 28
Worker  running with argument 29
Worker  running with argument 27
Worker  running with argument 30
Worker  running with argument 31
Worker  running with argument 32
Worker  running with argument 33
Worker  running with argument 34
Worker  running with argument 35
Worker  running with argument 36
Worker  running with argument 37
Worker  running with argument 38
Worker  running with argument 39
Worker  running with argument 40
Worker  running with argument 41
Worker  running with argument 42
Worker  running with argument 43
Worker  running with argument 44
Worker  running with argument 45
Worker  running with argument 46
Worker  running with argument 47
Worker  running with argument 48
Worker  running with argument 49
Worker  queue empty
Worker  queue empty
Worker  queue empty
Worker  queue empty
Worker  queue empty

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