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Stopping Threads Fermare un Processo

I'd like to start this page off with a question. How do you kill one thread from within another? Here's some code that shows the problem:

Ecco il codice che mostra come risolvere il problema:

   1 import threading
   2 import time
   3 
   4 class Worker(threading.Thread):
   5   def __init__(self, eventChannel, eventHandler):
   6     self.eventChannel = eventChannel
   7     self.eventHandler = eventHandler
   8     self.stopFlag = 0
   9 
  10   def shutdown(self):
  11     self.stopFlag = 1
  12 
  13   def run(self):
  14     self.stopFlag = 0
  15     while not self.stopFlag:
  16       event = self.eventChannel.waitEvent() # blocking call
  17       self.eventHandler.dispatchEvent(event)
  18 
  19 
  20 eventChannel = EventChannel()
  21 eventHandler = EventHandler()
  22 worker = Worker(eventChannel, eventHandler)
  23 worker.start()
  24 time.sleep(20)
  25 worker.shutdown()

The problem here is that EventChannel.waitEvent() is a blocking operation. So if no event ever arrives, then our worker thread never stops. (EventChannel and EventHandler are classes I've invented for this example)

Il costrutto o funzione EventChannel.waitEvent() è un blocco operativo. Così se un evento mai arriva, il nostro lavoro non fermerà mai il processo. Attenzione!!! Le (EventChannel and EventHandler sono classi da me inventate per questo esempio.

Suggestions Suggerimento

  def shutdown(self):
    self.stopFlag = 1
    self.eventChannel.push_event(NullEvent())

   1 import Queue, threading, traceback
   2 
   3 class StopMarker:
   4     """This is used as an individual stopper item."""
   5     
   6 class Worker(threading.Thread):
   7     """Get items from a queue and call the handler with the item.
   8     Errors in the handler are printed to stderr, the thread
   9     continues to run.
  10     An individual stop marker is used, so you can pass everyting
  11     as item (including None).
  12     """
  13     
  14     def __init__(self, handler):
  15         """Initialize Thread object and worker."""
  16         threading.Thread.__init__(self)
  17         self.running = 1
  18         self.handler = handler
  19         self.queue   = Queue.Queue()
  20         self.stopper = StopMarker()
  21     
  22     def run(self):
  23         """Worker loop. Errors in the handler are printed to
  24         stderr and the thread continues with the next item."""
  25         while self.running:
  26             try:
  27                 item = self.queue.get()
  28                 if item is self.stopper:
  29                     break
  30                 else:
  31                     self.handler(item)
  32             except:
  33                 traceback.print_exc()
  34     
  35     def stop(self):
  36         """Stop the worker thread and wait until it terminates.
  37         (Waits until last item is processed)"""
  38         self.queue.put(self.stopper)    #stopper item, then...
  39         self.join()                     #wait until the thread has shutdown
  40 
  41     def put(self, item):
  42         """Put an item in the queue to be processed by the handler."""
  43         self.queue.put(item)
  44 
  45 if __name__ == '__main__':
  46     def printer(item):
  47         print "printer(%r)" % item
  48     
  49     w = Worker(printer)
  50     w.start()
  51     for i in range(10):
  52         w.put(i)
  53     w.stop()

= Call to C function blocks all threads! !La chiamata ad una funzione C blocca tutti i processi=

I have a C module that does database queries. Those queries go off to an SQL server to be processed. I would like to use my query function within threads and to have it work like time.sleep(), that is, block the current thread until it finishes but allow other threads to continue operation. I haven't seen this issue addressed in any of the books I have.

Ho un modulo C che pone delle interrogazioni ad un Databases. Queste queries pongo a fermo un server SQL per essere processate. Voglio usare le mie funzioni querry all'interno dei processi e avere il lavoro come time.sleep(), se stesse in pausa, blocco il corrente processo finchè questo non ha finito, ma permetto ad altri processi di continuare le loro operazioni. Non vedo questa asserzione pubblicata in nessuno dei libri che possiedo.

" Ciò può essere attuato con il codice python. L'autore del D.B.

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