Queue in Python

A queue follows FIFO:
First In, First Out.

Real examples:

• ticketing systems
• print queues
• job scheduling
• message processing

Why not use list for queue?

Removing from front of list can be slow.
collections.deque is designed for fast ends.

Queue with deque

from collections import deque

q = deque()
q.append("Task1")     # enqueue
q.append("Task2")
print(q)

first = q.popleft()   # dequeue
print(first)
print(q)

Example: task processing simulation

from collections import deque

tasks = deque(["email", "report", "backup"])

while tasks:
    task = tasks.popleft()
    print("Processing:", task)

Graph: queue FIFO

flowchart LR
  A[Enqueue] --> B[Queue] --> C[Dequeue]

Remember

• Use deque for queues
• append + popleft
• queues are everywhere in systems