python正则实现计算器功能

本文实例为大家分享了python正则实现计算器功能的具体代码，供大家参考，具体内容如下

# -*- 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)