利用正则表达式实现计算器功能

 1 # 关键是匹配模式‘(([^()]+))’匹配括号内无括号的内容，分组和^很巧妙的实现了匹配括号以外的字符
 2 import re
 3 
 4 origin = '1 - 2 * ((60-30 + (-40.0/5) * (9-2*5/3+7/3*99/4*2998 +10*568/14)) - (-4*3)/(16-3*2))'
 5 
 6 def jisuan(args):
 7     value = eval(args)
 8     return value
 9 while True:
10     result= re.split('(([^()]+))',origin,1)
11     if len(result)==3:
12         before = result[0]
13         content = result[1]
14         after = result[2]
　　　　　　#上面等价于before，content，after = result
15         r = jisuan(content)
16         new_str = before + str(r) + after
17         origin = new_str
18     else:
19         print(jisuan(origin))
20         break