What is stack and it's methods ?

Stack

This lesson will introduce you to the stack data structure and its implementation in Python which we'll use in the problems throughout this chapter.

We'll cover the following
• What is a stack?
• Stack Operations • Push
• Pop
• Peek

In this lesson, we are going to consider the stack data structure and its implementation in Python.

In subsequent lessons, we’ll provide specific problems where a stack is particularly useful. We’ll be using the implementation that we develop in this lesson to solve those problems. 

What is stack?:-

First of all, let me describe what a stack is. Based on the name, it should be a relatively familiar concept.

Let’s assume that we have four books with the following riveting titles:

• A
• B
• C

At the moment, these books are strewn out all over the floor and we want to stack them up neatly.

Now we have a nice neat stack of books! If we want to retrieve a book from this stack, we can take the book on top. Taking a book from the bottom is a bit precarious and we don’t want to topple the entire stack. Therefore, we’ll take down the top book on the stack and read it or do whatever we want to do with it.

Let’s say we want to take Book A. Right now, it is at the bottom of the stack, so we need to take Book D, put it down, then do the same for Book C and Book B, and then we can access Book A.

This is the main idea of a stack. The data structure stack is very similar to a physical stack that you’d most likely be familiar with. The stack data structure allows us to place any programming artifact, variable or object on it just as our example stack allowed us to put books in it.

Stack Operations:-

Push:-

The operation to insert the data into the stack is called push. When we push the book on a stack, we put the book on the previous top element which means that the new book becomes the top element. This is what we mean when we use the push operation, we push elements onto a stack. We insert elements onto a stack and the last element to be pushed is the new top of the stack.

Pop:-

There is another operation that we can perform on the stack, popping. Popping is when we take the top book of the stack and put it down. This implies that when we remove an element from the stack, the stack follows the First-In, Last Out property. This means that the top element, the last to be inserted, is removed when we perform the pop operation.

Push and Pop are two fundamental routines that we’ll need for this data structure. 

Peek:- 

Another thing that we can do is view the top element of the stack so we can ask the data structure: “What’s the top element?” and it can give that to us using the peek operation. Note that the peek operation does not remove the top element, it merely returns it

We can also check whether or not the stack is empty, and a few other things too, that will come along the way as we implement it.

Code to create the stack in python:-

I hope you understand the basic concepts of a stack. Still, if you have any doubt so contact me from contact form I will respond to you within 24 hrs.

Happy Learning...