stackF_Harsh2255.py

# Python program for implementation of stack

# import maxsize from sys module
# Used to return -infinite when stack is empty
from sys import maxsize

# Function to create a stack. It initializes size of stack as 0
def createStack():
    stack = []
    return stack


# Stack is empty when stack size is 0
def isEmpty(stack):
    return len(stack) == 0


# Function to add an item to stack. It increases size by 1
def push(stack, item):
    stack.append(item)
    print(item + " pushed to stack ")


# Function to remove an item from stack. It decreases size by 1
def pop(stack):
    if isEmpty(stack):
        return str(-maxsize - 1)  # return minus infinite

    return stack.pop()


# Function to return the top from stack without removing it
def peek(stack):
    if isEmpty(stack):
        return str(-maxsize - 1)  # return minus infinite
    return stack[len(stack) - 1]


# Driver program to test above functions
stack = createStack()
push(stack, str(10))
push(stack, str(20))
push(stack, str(30))
print(pop(stack) + " popped from stack")