with上下文管理基础

 import queue
 import contextlib
 import time

 @contextlib.contextmanager
 def worker_state(xxx,val):
     xxx.append(val)
     print("before",xxx)
     try:
         time.sleep(1)
         yield
     finally:
         xxx.remove(val)
         print("after",xxx)

 if __name__ == '__main__':
     q = queue.Queue()
     q.put("")
     li = []
     with worker_state(li,1):
         q.get()