# Queue

## collections.dequeue

* queue: only supports removing elements from the back

* dequeue: also supports removing elements form the front

import collections

q = collections.deque([1, 2, 3], maxlen=None)

q.append(4)

q.extend([5, 6])

while q:

print(q.popleft())

## queue.Queue

* Used for synchronizing threads

* thread-safe

* Use collections.dequeue otherwise

import queue

q = queue.Queue(maxsize=0)

q.put(1)

q.put(2)

while not q.empty():

print(q.get())

# Priority queue

## heapq

* see heapq.txt

q = []

heapq.heappush(q, 3)

heapq.heappush(q, 1)

heapq.heappush(q, 2)

q = [3, 1, 2]

heapq.heapify(q) // in-place

while q:

print(heapq.heappop(q))

## queue.PriorityQueue

* For threads (like queue.Queue)

* Wrapper around heapq

pq = queue.PriorityQueue()

pq.put((1, "Task 1"))

pq.put((3, "Task 3"))

pq.put((2, "Task 2"))

print(pq.get()) # Output: (1, 'Task 1')

print(pq.get()) # Output: (2, 'Task 2')

print(pq.get()) # Output: (3, 'Task 3')