python正则实现计算器功能

# -*- coding: utf-8 -*- 
# Author :Gogh 
# @Time  :2017/12/4 20:16 
# @Email :361910002@qq.com 
import re 
def operator_update(formula): 
 # 对formula公式进行 去除空字符，更新运算符处理 
 formula = formula.replace(" ", "") # 去除空字符 
 formula = formula.replace("+-", "-") 
 formula = formula.replace("--", "+") 
 return formula 
 
 
def calc_muldiv(formula_list): 
 ''''' 
 计算公式里面的乘除 
 :param formula: 列表 
 :return: 
 ''' 
 for index, element in enumerate(formula_list): 
  if "*" in element or "/" in element: 
   operators = re.findall("[*/]", element) 
   calc_list = re.split("[*/]", element) 
   num = None 
   for i, e in enumerate(calc_list): 
    if num: 
     if operators[i - 1] == "*": 
      num *= float(e) 
     elif operators[i - 1] == "/": 
      num /= float(e) 
    else: 
     num = float(e) 
   formula_list[index] = num 
 return formula_list 
 
 
def calc_plumin(operators, num_list): 
 ''''' 
 计算列表数字的加减 
 :param operators: 运算符列表 
 :param num_list: 进行运算的数字列表 
 :return: 返回计算结果 
 ''' 
 num = None 
 for i, e in enumerate(num_list): 
  if num: 
   if operators[i - 1] == "+": 
    num += float(e) 
   elif operators[i - 1] == "-": 
    num -= float(e) 
  else: 
   num = float(e) 
 return num 
 
 
def merge(plus_minus_operator, multiply_divide_list): 
 ''''' 
 把列表中这样的形式'2*' '-3*' '5/3*' '4/2'合并到一块 
 :param formula_list: 
 :return: 
 ''' 
 for index, element in enumerate(multiply_divide_list): 
  if element.endswith("*") or element.endswith("/"): 
   multiply_divide_list[index] = element + plus_minus_operator[index] + multiply_divide_list[index + 1] 
   del multiply_divide_list[index + 1] 
   del plus_minus_operator[index] 
   return merge(plus_minus_operator, multiply_divide_list) 
 return plus_minus_operator, multiply_divide_list 
 
 
def bracket_calc(formula): 
 ''''' 
 对括号最内层的formula公式进行计算 
 :param formula: 
 :return: 
 ''' 
 formula = re.sub("[()]", "", formula) # 去除两边的（） 
 formula = operator_update(formula) 
 plus_minus_operator = re.findall("[+-]", formula) # 列表 '+' '-' 运算符 
 multiply_divide_list = re.split("[+-]", formula) # 列表 有'*' '/' 
 if multiply_divide_list[0] == "": # multiply_divide_list列表第一个字符为空的话，表示一个数字为负号 
  multiply_divide_list[1] = "-" + multiply_divide_list[1] 
  del plus_minus_operator[0] 
  del multiply_divide_list[0] 
 res = merge(plus_minus_operator, multiply_divide_list) 
 plus_minus_operator = res[0] # 列表 '+' '-' 运算符 进行合并处理 
 multiply_divide_list = res[1] 
 plus_minus_list = calc_muldiv(multiply_divide_list) # 生成只进行加减运算的列表 
 res = calc_plumin(plus_minus_operator, plus_minus_list) 
 return res 
 
 
def calculate(formula): 
 '''''计算程序主入口, 主要逻辑是先计算拓号里的值,算出来后再算乘除,再算加减''' 
 while True: 
  formula_depth = re.search("[()]+", formula) 
  if formula_depth: 
   formula_depth = formula_depth.group() 
   res = bracket_calc(formula_depth) 
   formula = formula.replace(formula_depth, str(res)) 
   print("\33[34;1m%s\33[0m" % (formula)) 
  else: 
   res = bracket_calc(formula) 
   print("\33[31;1m结果:%s\33[0m" % (res)) 
   exit() 
 
 
if __name__ == '__main__': 
 formula = "1 - 2 * ( (60-30 +(-9-2- 5-2*-3-5/3-40*4/2-3/5+6*3) * (-9-2-5-2*5/3 + 7 /3*99/4*2998 +10 * 568/14 )) -(-4*3)/ (16-3*2) )" 
 calculate(formula)