stack.py

stack=[]
top = None
def isempty(stack):
    if stack==[]:
        return True
    else:
        return False

#Function to push elements into the stack
def push(stk):
    item=eval(input("Enter the Name number price"))
    stk.append(item)
    top=len(stk)-1
    
#Function to pop elements from the stack
def pop(stk):
    if isempty(stack):
        print("Underflow")
    else:
        item=stk.pop()
        if len(stk)==0:
            top=None
        else:
            top=len(stk) - 1
        print("Popped Item = ", item)
        

#Function to display elements in the stack
def display(stk):
    if isempty(stack):
        print("Underflow")
    else:
        top=len(stk)-1
        print(stk[top],"<-top")
        for i in range (top-1,-1,-1):
             print(stk[i])


#Main program - Menu
while True:
    print("Stack Operations")
    print("1. Push")
    print("2. Pop")
    print("3. Display")
    print("4. Exit")
    ch=int(input("Enter your Choice"))
    if ch==1:
        push(stack)
    elif ch==2:
        pop(stack)
    elif ch==3:
        display(stack)
    elif ch==4:
        break
    else:
        print("Invalid Choice")