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)