gistfile1.txt

#!/usr/bin/env python

class Solution:

    def isOp(self, token):
        return token in ["+", "-", "*", "/"]

    def add(self, op1, op2):
        return op1 + op2

    def minus(self, op1, op2):
        return op1 - op2

    def multiply(self, op1, op2):
        return op1 * op2

    def divide(self, op1, op2):
        return op1 / op2

    # @param tokens, a list of string
    # @return an integer
    def evalRPN(self, tokens):
        l = []
        op_map = {
            "+": self.add,
            "-": self.minus,
            "*": self.multiply,
            "/": self.divide,
        }
        for token in tokens:
            if (self.isOp(token)):
                op2 = l.pop()
                op1 = l.pop()
                func = op_map[token]
                val = func(op1, op2)
                print "val", val, op1, op2
                l.append(val)
            else:
                l.append(int(token))


        return l.pop()