Hands-On Artificial Intelligence for Search

Stack data structure

A stack is a pile of objects placed one atop another (for example, a stack of books, a stack of clothes, or a stack of papers). There are two stacking operations: one for adding items to a stack, and one for removing items from a stack.

The operation used for adding items to a stack is called push, while the operation used for removing items is called as pop. Items are popped in the reverse order to push; that is why this data structure is called last-in first-out (LIFO).

Let's experiment with the stack data structure in Python. We'll be using the list data structure as a stack in Python. We'll use the append() method to push items to the stack and the pop() method to pop them out:

...stack = []print "stack", stack#add ...