Stack3

class Stack():

    def __init__(self):
        self.list = []

    def push(self,item):
        self.list.append(item)

    def pop(self):
        if len(self.list) > 0:
            return self.list.pop()
        else:
            print("list is empty")

    def isEmpty(self):
        return len(self.list) == 0

    def size(self):
        return len(self.list)

def postFixeval():
    print(" ***Postfix expression calcuation***")
    token = input("Enter Postfix expression : ").split()
    s = Stack()

    for i in token:
        if i in ('+','-','*','/'):
            op1,op2 = s.pop(),s.pop()
            if i == '+':
                s.push(op2+op1)
            elif i == '-':
                s.push(op2-op1)
            elif i == '*':
                s.push(op2*op1)
            elif i == '/':
                s.push(op2/op1)
        else:
            s.push(int(i))

    if not s.isEmpty():
        print("Answer : ",'{:.2f}'.format(s.pop()))
    else:
        print("list is empty")

postFixeval()