代码：
1 #!/usr/local/env python3 2 ''' 3 Author:@南非波波 4 Blog:http://www.cnblogs.com/songqingbo/ 5 E-mail:qingbo.song@gmail.com 6 ''' 7 8 import time,sys 9 import module 10 11 if __name__ == "__main__": 12 while True: 13 count = 0 14 if count < 3: 15 print(''' 16 请输入一个计算公式，类似下面格式： 17 ========================================================================================= 18 1 - 2 * ( (60-30 +(-40/5) * (9-2*5/3 + 7 /3*99/4*2998 +10 * 568/14 )) - (-4*3)/ (16-3*2) ) 19 ========================================================================================= 20 系统默认匹配所有的数字、(、)、+、-、/、*、. 21 计算器程序研发@南非波波 22 ''') 23 expression = input("请输入:").strip() #或取用户输入的表达式字符串，并去除左右的空格 24 # expression = "1 - 2 * ( (60-30 +(-40/5) * (9-2*5/3 + 7 /3*99/4*2998 +10 * 568/14 )) - (-4*3)/ (16-3*2) )" 25 expression = expression.replace(' ','') #去除字符串中间的空格，使用replace进行空字符串替换空格 26 if module.num_operator(expression): #成功匹配正确表达式 27 # print(expression) 28 result = module.recursion_bracket(expression) #将处理后没有括号的表达式赋值给expression 29 print(result) 30 break 31 else: 32 count += 1 33 print("你输入的表达式格式不正确!") 34 time.sleep(1) 35 continue 36 else: 37 print("你的输入错误次数已达三次,计算器将自动退出!感谢你的使用!") 38 time.sleep(1) 39 sys.exit(3)
1 #!/usr/local/env python3 2 ''' 3 Author:@南非波波 4 Blog:http://www.cnblogs.com/songqingbo/ 5 E-mail:qingbo.song@gmail.com 6 ''' 7 8 import re 9 10 #匹配一个表达式中的数字和运算符，如果匹配，返回expression，否则返回None 11 def num_operator(expression): 12 match_list = re.findall("[0-9]|(|)|+|-|*|/|.",expression) 13 if len(expression) == len(match_list): 14 return True 15 16 #特殊字符处理 17 def charmap(expression): 18 flag = True 19 while flag: 20 if expression.__contains__("++") or expression.__contains__("+-") or expression.__contains__("-+") or expression.__contains__("--"): 21 # match_str = re.search("d+.*d*(+-){1}d+.*d*",expression).group() 22 expression = expression.replace('+-','-') 23 expression = expression.replace('++','+') 24 expression = expression.replace('-+','-') 25 expression = expression.replace('--','+') 26 else: 27 flag = False 28 return expression 29 #操作加减 30 def compute_add_sub(expression): 31 ''' 32 expression表达式传进来的形式是(5+1-4)，左右成一对括号。所以这里需要将括号去掉 33 ''' 34 expression = expression.lstrip('(').rstrip(')') #去除表达式左右的括号 35 match_test = re.search("d+.*d*[+-]{1}d+.*d*",expression) 36 if not match_test: 37 return expression 38 else: 39 match_str = match_test.group() 40 if len(match_str.split('+')) > 1: 41 num1,num2 = match_str.split("+") 42 result = float(num1) + float(num2) 43 else: 44 num1,num2 = match_str.split("-") 45 result = float(num1) - float(num2) 46 exp_join = expression.split(match_str) 47 expression = "%s%s%s" % (exp_join[0],result,exp_join[1]) 48 return compute_add_sub(expression) 49 50 #操作乘除 51 def compute_mul_div(expression): 52 ''' 53 expression表达式传进来的形式是(9-2*5/3+7/3*99/4*2998+10*568/14)，左右成一对的括号。所以这里就需要将括号去掉然后递归处理乘除 54 ''' 55 expression = expression.lstrip('(').rstrip(')') #去除表达式左右的括号 56 match_test = re.search("d+.*d*[*/]+[+-]?d+.*d*",expression) 57 if not match_test: #判断是否能够匹配到* 或者 /。 58 return expression 59 else: 60 match_str = match_test.group() #获取到匹配的运算式，比如5/3，2*5 61 if len(match_str.split("/")) > 1: #计算除法 62 num1,num2 = match_str.split("/") 63 result = float(num1) / float(num2) 64 else: #计算乘法 len(match_str.split("*")) > 1 65 num1,num2 = match_str.split("*") 66 result = float(num1) * float(num2) 67 exp_join = expression.split(match_str) 68 expression = "%s%s%s" % (exp_join[0],result,exp_join[1]) 69 compute_mul_div(expression) #递归处理 70 return compute_mul_div(expression) 71 72 #处理优先级的执行 73 def compute_pri(expression): 74 expression = compute_mul_div(expression) #处理乘除 75 expression = charmap(expression) #处理特殊字符 76 expression = compute_add_sub(expression) #处理加减 77 return expression #返回一个值 78 79 #递归处理括号 80 def recursion_bracket(expression): 81 match_list = re.findall("(|)",expression) #匹配括号,如果存在递归处理 82 if not match_list: 83 # print(expression) 84 return compute_pri(expression) 85 else: 86 match_str = re.search("([^()]*)",expression) #匹配第一次出现的括号对 87 if match_str: 88 match_str = match_str.group() 89 # print("match_str:",match_str) 90 tmp = compute_pri(match_str) 91 expression = "%s%s%s" % (expression.split(match_str)[0],tmp,expression.split(match_str)[1]) #字符串拼接 92 # print("expression:",expression) 93 return recursion_bracket(expression) #递归处理括号 94 95 96 97 98 # expression = "(9-2*5/3+7/3*99/4*2998+10*568/14)" 99 # res = compute_pri(expression) 100 # print(res) 101 #递归处理括号 102 # def recursion_bracket(expression): 103 # match_list = re.findall("(|)",expression) #匹配括号,如果存在递归处理 104 # if match_list: 105 # tmp_list = [] #定义一个列表，存储左括号( 106 # res = '' 107 # for i in range(0, len(expression)): 108 # if expression[i] == "(": 109 # tmp_list.append(i) #获取括号出现的索引值列表 110 # print("tmp_list:",tmp_list) 111 # continue 112 # if expression[i] == ")" and tmp_list: 113 # ts = expression[tmp_list[-1]: i+1] 114 # if len(ts) > len(res): 115 # # ts = compute_mul_div(ts) 116 # # print(ts) 117 # # ts = charmap(ts) 118 # # ts = compute_add_sub(ts) 119 # res = ts 120 # print('i:%s,ts:%s' % (i,ts)) 121 # tmp_list.pop() 122 # print(tmp_list) 123 # print("res:",res) 124 # # return recursion_bracket(res) 125 # 126 # else: #匹配括号失败，返回表达式,做后续处理 127 # expression = compute_mul_div(expression) 128 # expression = charmap(expression) 129 # expression = compute_add_sub(expression)
github代码更新地址：https://github.com/swht/projects/tree/master/day04/计算器