Python Data Structures and Algorithms

Stacks

A stack is a data structure that is often likened to a stack of plates. If you have just washed a plate, you put it on top of the stack. When you need a plate, you take it off the top of the stack. So the last plate to be added to the stack will be the first to be removed from the stack. Thus, a stack is a last in, first out (LIFO) structure:

The preceding figure depicts a stack of plates. Adding a plate to the pile is only possible by leaving that plate on top of the pile. To remove a plate from the pile of plates means to remove the plate that is on top of the pile.

There are two primary operations that are done on stacks: push and ...