1 import re
2
3
4 def strip_operate(exp): # 合并多余的操作符
5 exp = exp.replace("+-", "-")
6 exp = exp.replace("--", "+")
7 return exp
8
9
10 def cal_exp_son(exp_son): # 计算两数的乘除
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): # 计算一个里面已经没有括号的式子
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: # 后加减
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)
