How Does Python Implement Queue Data Structure?


Angela Bailey

How Does Python Implement Queue Data Structure?

In computer science, a queue is a data structure that follows the First-In-First-Out (FIFO) principle. It is similar to a real-life queue, where the first person to join the line is the first one to be served.

Python provides a built-in module called collections that includes an implementation of the queue data structure called deque.

Deque: Double-Ended Queue

The deque class in Python’s collections module offers an optimized implementation of queues. It is called a double-ended queue because it allows elements to be added or removed from both ends.

Creating a Queue in Python

To create a queue using the deque class, you need to import the collections module and initialize an instance of deque with no arguments. Here’s how you can do it:

from collections import deque

queue = deque()

Adding Elements to the Queue

You can add elements to the queue using the append() method provided by deque. This method appends elements at the right end of the queue.


Removing Elements from the Queue

To remove elements from the queue, you can use either of these methods:

  • popleft(): Removes and returns the leftmost element from the queue.
  • pop(): Removes and returns the rightmost element from the queue.

element = queue.popleft()
element = queue.pop()

Checking if the Queue is Empty

You can check whether the queue is empty or not using the not keyword, which returns True if the queue is empty and False otherwise.

if not queue:
    print("Queue is empty")
    print("Queue is not empty")

Accessing Elements in the Queue

The deque class allows you to access elements in the queue by index. However, please note that accessing elements in the middle of the queue has a time complexity of O(n), where n is the number of elements in the queue.

element = queue[index]


Python’s deque class provides an efficient implementation of queues using a double-ended approach. By utilizing methods like append(), popleft(), and pop(), you can add, remove, and access elements from both ends of the queue.

With these capabilities, Python makes it easy to work with queues in your programs.

If you want to learn more about Python’s data structures and algorithms, make sure to check out our other articles!

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