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()