Stack & Queue in Python

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1. Stack Implementation

In Python, you can easily use a List as a stack using append() and pop().

stack = []

# Push
stack.append("A")
stack.append("B")

# Pop
print(stack.pop()) # "B"
print(stack.pop()) # "A"

2. Queue Implementation

For a queue, using a standard list is inefficient (because deleting the first item requires shifting all other items). Instead, use collections.deque.

from collections import deque

queue = deque()

# Enqueue
queue.append("First")
queue.append("Second")

# Dequeue
print(queue.popleft()) # "First"
print(queue.popleft()) # "Second"

Summary Comparison

Data Structure	Logic	Python Recommended Tool
Stack	LIFO	list (append/pop)
Queue	FIFO	collections.deque (append/popleft)

Performance

collections.deque is optimized for fast appends and pops from both ends.