Method weakref_cb

Lib/concurrent/futures/thread.py:226–227

(_, q=self._work_queue)

        # When the executor gets lost, the weakref callback will wake up
        # the worker threads.
        def weakref_cb(_, q=self._work_queue):
            q.put(None)

        num_threads = len(self._threads)
        if num_threads < self._max_workers: