Stack Data Structure in Python

A great analogy we can utilize is stacking a heap of books. We tend to ceaselessly keep a shiny new book on top and take away the top most book

What is a stack ?

Stack is a linear data structure which stores items using Last In, First Out(LIFO)strategy. Whenever a new element is added to a stack, it is added to the highest point of the stack, and the top element is taken out first from the stack.

Stack in Python can be executed in following ways:

• List
• collections.deque
• queue.LifoQueue

Some of the functions related with stack are:

• push():When this function is called, new element is added at the top of the stack
• pop():This function removes the top most element of the stack
• empty():Return True if the stack is empty else returns False
• peek(): This function returns the top element of the stack

Implementation of Stack

class Stack():
    def __init__(self):
        self.items = []
    def push(self, item):
        self.items.append(item)
    def pop(self):
        return self.items.pop()
    def is_empty(self):
        return self.items == []
    def peek(self):
        if not self.is_empty():
            return self.items[-1]        
    def get_stack(self):
        return self.items
s=Stack()
print("Stack is Empty:",s.is_empty())
s.push("A")
s.push("B")
s.push("C")
s.push("D")
s.push("E")
s.push("F")
print("Stack after appending =",s.get_stack())
s.pop()
s.pop()
print("Stack after removing elements =",s.get_stack())
print("Peek element =",s.peek())

Output:

Stack is Empty: True
Stack after appending = ['A', 'B', 'C', 'D', 'E', 'F']
Stack after removing elements = ['A', 'B', 'C', 'D']
Peek element = D