Stack Basics — LIFO for Students

A stack is last-in-first-out (LIFO): you add (push) and remove (pop) from the same end—the top.

Try this in Python

stack: list[int] = []
stack.append(1)
stack.append(2)
stack.append(3)
print(stack.pop(), stack.pop(), stack.pop())

Key takeaways

• Think of one open end only.
• In Python, list.append + list.pop() is the usual student stack.
• Never pop(0) if you care about speed—that is a queue pattern, not a stack.