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%s33[0m" % (formula)) 
    else: 
      res = bracket_calc(formula) 
      print("33[31;1m结果:%s33[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)