Joel's

objCalc

operators = ['+', '-', '*', '/']

class Expression():
    def __init__(self, input_ss):
        self.input_ss = input_ss

    def eval(self):
        for op in operators:
            if op in ['+', '-']:
                result = 0
            if op in ['*', '/']:
                result = 1
            if len(self.input_ss.split(op)) > 1:
                sub_expression_strings = self.input_ss.split(op)
                for ss in sub_expression_strings:
                    result = do_op(result, op, Expression(ss).eval())
                return result

        # this is only called if the substring had no operators
        return int(self.input_ss) * 1.0

def do_op(initial, operator, number):
    if operator == '+':
        return initial + number
    if operator == '-':
        return initial - number
    if operator == '*':
        return initial * number
    if operator == '/':
        return initial / number