ThreadPoolExecutor: how to limit the queue maxsize?

Python’s ThreadPoolExecutor doesn’t have the feature you’re looking for, but the provided class can be easily sub-classed as follows to provide it:

from concurrent import futures
import queue

class ThreadPoolExecutorWithQueueSizeLimit(futures.ThreadPoolExecutor):
    def __init__(self, maxsize=50, *args, **kwargs):
        super(ThreadPoolExecutorWithQueueSizeLimit, self).__init__(*args, **kwargs)
        self._work_queue = queue.Queue(maxsize=maxsize)