Implement a FIFO Message Queue in Python with deque

This code implements a FIFO (first-in-first-out) message queue class using Python's collections.deque, providing enqueue, dequeue, peek, and size operations.

Easy Python 3.6+ Aug 9, 2026 Streaming & messaging 14 views 0 copies

queue deque fifo collections messaging

Python code

44 lines

Python 3.6+

from collections import deque

class MessageQueue:
    def __init__(self):
        self.queue = deque()

    def enqueue(self, message):
        self.queue.append(message)
        print(f"Enqueued: {message}")

    def dequeue(self):
        if self.is_empty():
            print("Queue is empty, cannot dequeue.")
            return None
        message = self.queue.popleft()
        print(f"Dequeued: {message}")
        return message

    def peek(self):
        if self.is_empty():
            print("Queue is empty, nothing to peek.")
            return None
        message = self.queue[0]
        print(f"Front of queue: {message}")
        return message

    def is_empty(self):
        return len(self.queue) == 0

    def size(self):
        print(f"Queue size: {len(self.queue)}")
        return len(self.queue)

if __name__ == "__main__":
    mq = MessageQueue()
    mq.enqueue("Message 1")
    mq.enqueue("Message 2")
    mq.enqueue("Message 3")
    mq.peek()
    mq.size()
    mq.dequeue()
    mq.dequeue()
    mq.dequeue()
    mq.dequeue()

Output

stdout

Enqueued: Message 1
Enqueued: Message 2
Enqueued: Message 3
Front of queue: Message 1
Queue size: 3
Dequeued: Message 1
Dequeued: Message 2
Dequeued: Message 3
Queue is empty, cannot dequeue.

How it works

The deque provides O(1) append and popleft operations, making it an efficient structure for a FIFO queue as opposed to a list where popping from the front is O(n). The enqueue method appends to the right, while dequeue removes from the left, preserving order. The peek method returns the front element without removal, and is_empty checks the queue's length. This class encapsulates the queue logic, allowing easy reuse in larger applications.

Common mistakes

Using a list and pop(0) which is O(n) instead of deque.popleft()
Not handling dequeue/peek on an empty queue, leading to IndexError
Forgetting to check the queue size before dequeue in concurrent scenarios
Using appendleft for enqueue which reverses the FIFO order

Variations

Use queue.Queue from the standard library for thread-safe FIFO operations
Implement with a list and an index pointer to avoid shifting elements

Real-world use cases

Managing a task queue in a multi-threaded application to process jobs in order.
Buffering messages in a microservice before batch processing for ordered delivery.
Implementing a request queue for an API gateway to balance load sequentially.

Implement a FIFO Message Queue in Python with deque

Python code

Output

How it works

Common mistakes

Variations

Real-world use cases

More from Streaming & messaging

Tutorials

Quizzes

Python code

Output

How it works

Common mistakes

Variations

Real-world use cases

More from Streaming & messaging

Keep learning

Tutorials

Quizzes