TDD表达式再次实现（待完善）

def num(s, idx):    return int(s[idx])def plus(s):    return num(s,0) + num(s,2)def cur(s, idx):    return s[idx]def plus2(s):    v = num(s, 0)    i = 1    op = cur(s, i)    while (op == '+'):        if (i + 1 < len(s)):            i += 1            v += num(s, i)        else:            break        if (i + 1 < len(s)):            i += 1            op = cur(s, i)          else:            break    return v

#!/usr/bin/env python# -*- coding:utf-8 -*-# Filename:test_expr.pyimport unittestfrom expression2 import *class ExprTestCase(unittest.TestCase):    def setUp(self):        return    def tearDown(self):        return    def testNum(self):        self.assertEqual(1, num("1", 0))        self.assertEqual(3, num("1+3", 2))        self.assertEqual(5, num("1+3+5", 4))        return True    def testPlus(self):        self.assertEqual(4, plus("1+3"))        self.assertEqual(9, plus2("1+3+5"))              if __name__ == '__main__':    unittest.main()