Explain the differences between the stack data structure and the queue data structure.

Stack and queue are data structures that differ in the order of element processing:

• Stack operates on the LIFO (Last In, First Out) principle — the last added element is retrieved first. Imagine a stack of plates: you take the top plate, which was placed last.

• Queue operates on the FIFO (First In, First Out) principle — the first added element is retrieved first. It's similar to a line in a store: the first customer to arrive is served first.

In Python, a stack can be implemented using a list, with the append() method to add and pop() to remove from the end:

stack = []
stack.append(1)  # add element
stack.append(2)
print(stack.pop())  # retrieve the last added element, outputs 2

A queue can be implemented using collections.deque, which is efficient for adding and removing elements from both ends:

from collections import deque
queue = deque()
queue.append(1)  # add element to the end
queue.append(2)
print(queue.popleft())  # retrieve the first added element, outputs 1