Clear all items from the queue

PythonQueue

Python Problem Overview


How can I clear a queue. For example I have datas in a queue, but for some reason I don't need the existing data, and just want to clear the queue.

Is there any way? Will this work:

oldQueue = Queue.Queue()

Python Solutions


Solution 1 - Python

q = Queue.Queue()
q.queue.clear()

EDIT I omitted the issue of thread safety for clarity and brevity, but @Dan D is quite correct, the following is better.

q = Queue.Queue()
with q.mutex:
    q.queue.clear()

Solution 2 - Python

You just can not clear the queue, because every put also add the unfinished_tasks member. The join method depends on this value. And all_tasks_done needs to be notified also.

q.mutex.acquire()
q.queue.clear()
q.all_tasks_done.notify_all()
q.unfinished_tasks = 0
q.mutex.release()

or in decent way, use get and task_done pair to safely clear the tasks.

while not q.empty():
    try:
        q.get(False)
    except Empty:
        continue
    q.task_done()

or just create a new Queue and delete old one.

Solution 3 - Python

This seems to do it pretty well for me. I welcome comments/additions in case I missed anything important.

class Queue(queue.Queue):
  '''
  A custom queue subclass that provides a :meth:`clear` method.
  '''

  def clear(self):
    '''
    Clears all items from the queue.
    '''

    with self.mutex:
      unfinished = self.unfinished_tasks - len(self.queue)
      if unfinished <= 0:
        if unfinished < 0:
          raise ValueError('task_done() called too many times')
        self.all_tasks_done.notify_all()
      self.unfinished_tasks = unfinished
      self.queue.clear()
      self.not_full.notify_all()

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Content TypeOriginal AuthorOriginal Content on Stackoverflow
QuestionOHL&#193;L&#193;View Question on Stackoverflow
Solution 1 - PythonRob CowieView Answer on Stackoverflow
Solution 2 - PythonV.E.OView Answer on Stackoverflow
Solution 3 - PythonNiklas RView Answer on Stackoverflow