1 import re
 2 
 3 
 4 def strip_operate(exp):    # 合並多余的操作符
 5     exp = exp.replace("+-", "-")
 6     exp = exp.replace("--", "+")
 7     return exp  
 8 
 9 
10 def cal_exp_son(exp_son):    # 計算兩數的乘除
11     if "/" in exp_son:
12         a, b = exp_son.split("/")
13         return str(float(a)/float(b))
 
14     elif "*" in exp_son:
15         a, b = exp_son.split("*")
16         return str(float(a)*float(b))
17 
18 
19 def cal_no_bracket(exp):    # 計算一個裏面已經沒有括號的式子
20     exp = exp.strip("()")
21     while True:
22         ret1 = re.search(r"\d+\.?\d*[/*]-?\d+\.?\d*", exp)
23         if ret1:     # 先乘除
 

24             exp_son = ret1.group()
25             ret2 =cal_exp_son(exp_son)
26             exp = exp.replace(exp_son, ret2)
27             exp = strip_operate(exp)
28         else:      # 後加減
29             ret4 = re.findall(r"-?\d+\.?\d*", exp)
30             sum1 = 0
31             for i in ret4:
 
32                 sum1 += float(i)
33             return str(sum1)
34 
35 
36 def main_1(express):
37     while True:
38         ret = re.search(r"\([^()]+\)", express)
39         if ret:
40             express_no_bracket = ret.group()    
41             ret3 = cal_no_bracket(express_no_bracket)
42             express = express.replace(express_no_bracket, ret3)
43             express = strip_operate(express)
44         else:
45             ret4 = cal_no_bracket(express)
46             return ret4
47 
48 
49 express = ‘1 - 2 * ( (60-30 +(-40/5) * (9-2*5/3 + 7 /3*99/4*2998 +10 * 568/14 )) - (-4*3)/ (16-3*2) )‘
50 express = express.replace(" ", "")
51 ret5 = main_1(express)
52 print(ret5)

python實現計算器功能