rstring.py

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

# Function to determine the size of the stack
def size(stack):
	return len(stack)

# Stack is empty if the size is 0
def isEmpty(stack):
	if size(stack) == 0:
		return true

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

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

# A stack based function to reverse a string
def reverse(string):
	n = len(string)

	# Create a empty stack
	stack = createStack()

	# Push all characters of string to stack
	for i in range(0, n, 1):
		push(stack, string[i])

	# Making the string empty since all
	# characters are saved in stack
	string = ""

	# Pop all characters of string and put
	# them back to string
	for i in range(0, n, 1):
		string += pop(stack)

	return string


# Driver code
s = "string"
print("The original string is : ", end="")
print(s)
print("The reversed string(using stack) is : ", end="")
print(reverse(s))