Evaluate Reverse Polish Notation

class Solution:
    def evalRPN(self, tokens: List[str]) -> int:
        stack=[]
        for i in tokens:
            if i == "+":
                  stack.append(stack.pop()+ stack.pop())

            elif   i=="*":
                stack.append(stack.pop()*stack.pop())
            elif  i=="-":
                a=stack.pop()
                b=stack.pop()
                stack.append(b-a)
            elif i=="/":
                a=stack.pop()
                b=stack.pop()
                stack.append(int(b/a))
            else :
                stack.append(int(i))
        return stack[0]