python regular calculator function

This article is an example to share python regular calculator function of the specific code for your reference, the specific content is as follows

# -*- coding: utf-8 -*- 
# Author :Gogh 
# @Time  :2017/12/4 20:16 
# @Email :361910002@qq.com 
import re 
def operator_update(formula): 
 #  right formula formula   Remove null characters and update operator processing  
 formula = formula.replace(" ", "") #  Null-out character  
 formula = formula.replace("+-", "-") 
 formula = formula.replace("--", "+") 
 return formula 
 
 
def calc_muldiv(formula_list): 
 ''''' 
  Calculate the multiplication and division in the formula  
 :param formula:  The list of  
 :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): 
 ''''' 
  Calculate the addition and subtraction of list Numbers  
 :param operators:  Operator list  
 :param num_list:  A list of Numbers to perform an operation on  
 :return:  Return the calculated result  
 ''' 
 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): 
 ''''' 
  Put the list in this form '2*' '-3*' '5/3*' '4/2' Incorporated into the 1 block  
 :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): 
 ''''' 
  The innermost pair of parentheses formula Formula calculation  
 :param formula: 
 :return: 
 ''' 
 formula = re.sub("[()]", "", formula) #  Get rid of the () on both sides  
 formula = operator_update(formula) 
 plus_minus_operator = re.findall("[+-]", formula) #  The list of  '+' '-'  The operator  
 multiply_divide_list = re.split("[+-]", formula) #  The list of   There are '*' '/' 
 if multiply_divide_list[0] == "": # multiply_divide_list The list of the first 1 If a character is empty, it means 1 The Numbers are negative  
  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] #  The list of  '+' '-'  The operator   Merge processing  
 multiply_divide_list = res[1] 
 plus_minus_list = calc_muldiv(multiply_divide_list) #  Generates a list that only adds and subtracts  
 res = calc_plumin(plus_minus_operator, plus_minus_list) 
 return res 
 
 
def calculate(formula): 
 ''''' Compute program main entry ,  The main logic is to compute the value in the extension first , And then we can multiply and divide , Then the add and subtract ''' 
 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 The results of :%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)