Hi, I thought maybe a callback before the worker of a Executor finishes would be helpful. It would allow the setup and teardown resources (such as file, databases, connections, ...) across workers. My particular use case is for closing down requests.Session objects, that currently its very complicated to cleanup properly. There are many other use cases, a generic format would be something like the following: import threading from concurrent.futures import ThreadPoolExecutor worker_local = threading.local() def session_initializer(): # Initialize costly resources for a particular worker worker_local.resources = ... def session_deinitializer(): # Deinitialize worker resources carefully worker_local.resources ... with ThreadPoolExecutor(initializer=session_initializer, deinitializer=session_deinitializer) as executor: executor.submit(task) ...