threading.BoundedSemaphore

import time
lst=[]
lock=threading.BoundedSemaphore(2)
def fun(arg):
    lock.acquire()
    print(arg)
    # lst.append(arg)
    time.sleep(1)
    # m=lst[-1]
    lock.release()
for i in range(10):
    t=threading.Thread(target=fun,args=(i,))
    t.start()