Concepts

Computer Science - Class 12
Chapter 3 - Stacks

We can implement a stack using a list in Python , as a list is a dynamic data structure that can grow or shrink as needed.

We can use the built-in methods of list, such as append and pop , to perform push and pop operations on the stack.

We can also use the len function to get the size of the stack, and check if it is empty or full.

Here is an example of how to implement a stack using a list in Python:

• ## create an empty list to store the stack elements

``` stack = [] ```

• ## define a function to push an element to the stack

``` def push(element):  ```

``` # append the element to the end of the list  ```

``` stack.append(element)  ```

``` # print a message to indicate successful operation  ```

``` print(element, “pushed to stack”) ```

• ## define a function to pop an element from the stack

``` def pop():  ```

``` # check if the stack is empty  ```

``` if len(stack) == 0:  ```

``` # print a message to indicate error  ```

``` print(“Stack is empty”)  ```

``` # return None  ```

``` return None  ```

``` else:  ```

``` # pop and return the last element of the list  ```

``` element = stack.pop()  ```

``` # print a message to indicate successful operation  ```

``` print(element, “popped from stack”)  ```

``` # return the element  ```

``` return element ```

• ## test the functions

``` push(10) # 10 pushed to stack  ```

``` push(20) # 20 pushed to stack  ```

``` push(30) # 30 pushed to stack  ```

``` pop() # 30 popped from stack  ```

``` pop() # 20 popped from stack  ```

``` pop() # 10 popped from stack  ```

``` pop() # Stack is empty ```

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