需求描述：
1、实现加减乘除及拓号优先级解析
2、用户输入 1 - 2 * ( (60-30 +(-40/5) * (9-2*5/3 + 7 /3*99/4*2998 +10 * 568/14 )) - (-4*3)/ (16-3*2) )等类似公式后，必须自己解析里面的(),+,-,*,/符号和公式，运算后得出结果
实现代码：
1 import re 2 import functools 3 4 5 def minus_operator_handler(formula): 6 '''处理一些特殊的减号运算''' 7 minus_operators = re.split("-",formula) 8 calc_list= re.findall("[0-9]",formula) 9 if minus_operators[0] == '': #第一值肯定是负号 10 calc_list[0] = '-%s' % calc_list[0] 11 res = functools.reduce(lambda x,y:float(x) - float(y), calc_list) 12 print("\033[33;1m减号[%s]处理结果:\033[0m" % formula, res ) 13 return res 14 15 def remove_duplicates(formula): 16 formula = formula.replace("++","+") 17 formula = formula.replace("+-","-") 18 formula = formula.replace("-+","-") 19 formula = formula.replace("--","+") 20 formula = formula.replace("- -","+") 21 return formula 22 def compute_mutiply_and_dividend(formula): 23 '''算乘除,传进来的是字符串噢''' 24 operators = re.findall("[*/]", formula ) 25 calc_list = re.split("[*/]", formula ) 26 res = None 27 for index,i in enumerate(calc_list): 28 if res: 29 if operators[index-1] == "*": 30 res *= float(i) 31 elif operators[index-1] == "/": 32 res /= float(i) 33 else: 34 res = float(i) 35 36 print("\033[31;1m[%s]运算结果=\033[0m" %formula, res ) 37 return res 38 def handle_minus_in_list(operator_list,calc_list): 39 '''有的时候把算术符和值分开后,会出现这种情况 ['-', '-', '-'] [' ', '14969037.996825399 ', ' ', '12.0/ 10.0 '] 40 这需要把第2个列表中的空格都变成负号并与其后面的值拼起来,恶心死了 41 ''' 42 for index,i in enumerate(calc_list): 43 if i == '': #它其实是代表负号,改成负号 44 calc_list[index+1] = i + calc_list[index+1].strip() 45 def handle_special_occactions(plus_and_minus_operators,multiply_and_dividend): 46 '''有时会出现这种情况 , ['-', '-'] ['1 ', ' 2 * ', '14969036.7968254'],2*...后面这段实际是 2*-14969036.7968254,需要特别处理下,太恶心了''' 47 for index,i in enumerate(multiply_and_dividend): 48 i = i.strip() 49 if i.endswith("*") or i.endswith("/"): 50 multiply_and_dividend[index] = multiply_and_dividend[index] + plus_and_minus_operators[index] + multiply_and_dividend[index+1] 51 del multiply_and_dividend[index+1] 52 del plus_and_minus_operators[index] 53 return plus_and_minus_operators,multiply_and_dividend 54 def compute(formula): 55 '''这里计算是的不带括号的公式''' 56 57 formula = formula.strip("()") #去除外面包的拓号 58 formula = remove_duplicates(formula) #去除外重复的+-号 59 plus_and_minus_operators = re.findall("[+-]", formula) 60 multiply_and_dividend = re.split("[+-]", formula) #取出乘除公式 61 if len(multiply_and_dividend[0].strip()) == 0:#代表这肯定是个减号 62 multiply_and_dividend[1] = plus_and_minus_operators[0] + multiply_and_dividend[1] 63 del multiply_and_dividend[0] 64 del plus_and_minus_operators[0] 65 66 plus_and_minus_operators,multiply_and_dividend=handle_special_occactions(plus_and_minus_operators,multiply_and_dividend) 67 for index,i in enumerate(multiply_and_dividend): 68 if re.search("[*/]" ,i): 69 sub_res = compute_mutiply_and_dividend(i) 70 multiply_and_dividend[index] = sub_res 71 72 #开始运算+,- 73 print(multiply_and_dividend, plus_and_minus_operators) 74 total_res = None 75 for index,item in enumerate(multiply_and_dividend): 76 if total_res: #代表不是第一次循环 77 if plus_and_minus_operators[index-1] == '+': 78 total_res += float(item) 79 elif plus_and_minus_operators[index-1] == '-': 80 total_res -= float(item) 81 else: 82 total_res = float(item) 83 print("\033[32;1m[%s]运算结果:\033[0m" %formula,total_res) 84 return total_res 85 86 def calc(formula): 87 '''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''' 88 parenthesise_flag = True 89 calc_res = None #初始化运算结果为None,还没开始运算呢,当然为None啦 90 while parenthesise_flag: 91 m = re.search("\([^()]*\)", formula) #找到最里层的拓号 92 if m: 93 #print("先算拓号里的值:",m.group()) 94 sub_res = compute(m.group()) 95 formula = formula.replace(m.group(),str(sub_res)) 96 else: 97 print('\033[41;1m----没拓号了...---\033[0m') 98 99 print('\n\n\033[42;1m最终结果:\033[0m',compute(formula)) 100 parenthesise_flag = False #代表公式里的拓号已经都被剥除啦 101 102 if __name__ == '__main__': 103 104 #res = calc("1 - 2 * ( (60-30 +(-40/5) * (9-2*5/3 + 7 /3*99/4*2998 +10 * 568/14 )) - (-4*3)/ (16-3*2) )") 105 res = calc("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) )")