python - Reduce the number of active threads created by ThreadPoolExecutor? -

for threadpoolexecutor, want monitor number of threads running. seems impossible. number of active threads continually increasing. normal thread, if target function returns, thread shutdown.

import threading, concurrent.futures  def test():     pass  p_ac=threading.active_count() #number of threads=2  #for threads trs=[none]*10 in range(10):     trs[i]=threading.thread(target=test)     trs[i].start  print(threading.active_count()==p_ac) #true  #for executor executor=concurrent.futures.threadpoolexecutor(10) _ in range(10):     executor.submit(test) print(threading.active_count()) #number of threads=12 

the threadpoolexecutor does not shutdown threads when active. threadpoolexecutor(x) creates x threads , keeps them alive until shutdown executor via executor.shutdown() or executor decides doesn't need many threads. anyway x expected amount of threads if executor active.