1 # Author : Kelvin
2 # Date : 2019/1/10 12:36
3
4 # 实现计算器功能（加减乘除） 例如：2+(5*2)-(6/2*(5-1))) 4+2*3 1+（2*（3-1））+(2*(1+2))
5 import re
6 #①计算不包含括号的运算
7 def simple(equation):
8 # 先判断是否存在 * / 运算
9 flag=re.findall("\*|\/",equation)
10 if flag:
11 res_s1 = re.findall("(\d+\.\d+|\d+|\+|\-|\*|\/)", equation) #查找所有的数字 加减乘除符号
12 # print("simple:", res_s1)
13 list_dig1 = [i for i in res_s1 if i not in ["+", "-", "*", "/"]]
14 list_mod1 = [i for i in res_s1 if i in ["+", "-", "*", "/"]]
15 for i in range(len(list_mod1)):
16 if list_mod1[i] in ["/", "*"]:
17 mul1 = list_dig1[i]
18 mul2 = list_dig1[i + 1]
19 if list_mod1[i] is "/":
20 list_list1 = [mul1, "/", mul2]
21 res_str1 = "".join(list_list1)
22 # print(res_str)
23 res_res1 = str(float(mul1) / float(mul2))
24 # print(res_res1)
25 # print(type(res_res1))
26 equation = equation.replace(res_str1, res_res1)
27 # print(equation)
28 else:
29 if list_mod1[i] is "*":
30 list_list1 = [mul1, "*", mul2]
31 res_str = "".join(list_list1)
32 # print(res_str)
33 res_res1 = str(float(mul1) * float(mul2))
34 # print(res_res1)
35 # print(type(res_res1))
36 equation = equation.replace(res_str, res_res1)
37 # print(equation)
38 #下面是处理没有 * / 之后的运算
39 res_s2 = re.findall("(\d+\.\d+|\d+|\+|\-)", equation)
40 # print("+ -:", res_s2)
41 list_dig2 = [i for i in res_s2 if i not in ["+", "-"]]
42 list_mod2 = [i for i in res_s2 if i in ["+", "-"]]
43 result=list_dig2[0]
44 # print(list_dig2)
45 # print(list_mod2)
46 for i in range(1,len(list_dig2)):
47 m=list_mod2[i-1]
48 if m=="+":
49 result=float(result)+float(list_dig2[i])
50 else:
51 result=float(result)-float(list_dig2[i])
52 # print("最终结果：",result)
53 return result
54
55
56
57
58 #②计算包含括号的运算
59 def trouble(equation):
60 tro_res1=re.findall("\([^()]*\)",equation)
61 # print(tro_res1)
62 if tro_res1:
63 for i in tro_res1:
64 a=re.findall("[^(^)]",i)
65 b="".join(i)
66 # print("b:",b)
67 res_temp=str(simple(b))
68 equation=equation.replace(i,res_temp)
69 # print(equation)
70 # print(equation)
71 else:
72 return simple(equation)
73
74 return trouble(equation) #递归调用trouble函数，直到所有括号全部处理完毕
75
76
77
78
79
80 #③计算器的主方法
81 def cal(equation):
82 equation = equation.replace(" ", "") # 去除算式字符串中的空格 （过滤杂质）
83 res1=re.findall("[a-zA-Z@$%^&!]",equation)
84 # print(res1)
85 if res1:
86 print("算式输入有误，请重试！")
87 else:
88 cal_flag=re.findall("\(",equation)
89 if cal_flag:
90 return trouble(equation)
91 else:
92 return simple(equation)
93
94
95
96 #④测试代码
97 if __name__=="__main__":
98 s = input("请输入算式：")
99 result=cal(s)
100 print("%s 运算结果："%s,result)
101 # 1+(2*(2+1))+(2/(4*2))运算结果： 7.25 1+(2+4*2)运算结果： 11.0 1+(2*(2+1))+(2/(4*2))-(2-(4/(2*2)))运算结果： 6.25
