计算器

Posted 2020-09-15 高卓

开发一个简单的python计算器

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(不能调用eval等类似功能偷懒实现)，运算后得出结果，结果必须与真实的计算器所得出的结果一致

 1 #1-2*((60-30+(-40/5)*(9-2*5/3+7/3*99/4*2998+10*568/14))-(-4*3)/(16-3*2))
 2 import re
 3 
 4 def choice():
 5     #得到用户输入的算式
 6     num = ‘‘.join(input(‘计算器启动:‘).split())
 7     #进入循环拆分
 8     while True:
 9         if ‘(‘ in num:
10             ct = re.search(r‘\(([^()]+)\)‘, num)
11             if ct is not None:
12                 b = ct.groups()[0]
13                 c = count(b)
14                 num = re.sub(r‘\(([^()]+)\)‘, str(c), num, 1)
15         else:
16             c = count(num)
17             print(c)
18             break
19 # 乘除式
20 def mul(num):
21     b = re.search(r‘\d+\.?\d*(\*-?\d+\.?\d*)+‘, num)
22     if b is not None:
23         b = b.group()
24         rest = 1
25         c = re.findall(r‘-?\d+\.?\d*‘, b)
26         ls = []
27         for item in c:
28             ls.append(float(item))
29         for i1 in range(len(ls)):
30             rest = rest * ls[i1]
31         a = re.sub(r‘\d+\.?\d*(\*-?\d+\.?\d*)+‘, str(rest), num, 1)
32         return a
33 #加减法
34 def add(num):
35     if ‘--‘ in num:
36         num = num.replace(‘--‘, ‘+‘)
37     c = re.findall(r‘-?\d+\.?\d*‘, num)
38     ls = []
39     for i in c:
40         ls.append(float(i))
41     rest = sum(ls)
42     return rest
43 #开始计算
44 def run(num):
45     b = re.search(r‘\d+\.?\d*(\/-?\d+\.?\d*)+‘, num)
46     if b is not None:
47         b = b.group()
48         c = re.findall(r‘-?\d+\.?\d*‘, b)
49         ls =[]
50         for i in c:
51             ls.append(float(i))
52         rest = ls[0]
53         for i1 in range(1,len(ls)):
54             rest = rest / ls[i1]
55         num = re.sub(r‘\d+\.?\d*(\/-?\d+\.?\d*)+‘, str(rest), num, 1)
56         return num
57 #得到结果
58 def count(b):
59     while True:
60         if ‘*‘ in b:
61             c = b.split(‘*‘)
62             if ‘/‘ in c[0]:
63                 b = run(b)
64             else:
65                 b = mul(b)
66         elif ‘/‘ in b:
67             b = run(b)
68 
69         elif ‘+‘ or ‘-‘ in b:
70             b = add(b)
71             return b
72         else:
73             return b
74 choice()