剑指Offer 20 表示数值的字符串

请实现一个函数用来判断字符串是否表示数值（包括整数和小数）。例如，字符串"+100","5e2","-123","3.1416"和"-1E-16"都表示数值。但是"12e","1a3.14","1.2.3","+-5"和"12e+4.3"都不是。

 1 # -*- coding:utf-8 -*-
 2 import re
 3 class Solution:
 4     # s字符串
 5     def isNumeric(self, s):
 6         if len(s) == 0:
 7             return False
 8         pattern = '[+-]?d*(.d+)?([eE][+-]?d+)?'
 9         result = re.search(pattern,s)
10         if result != None and result.span() == (0,len(s)):
11             return True
12         else:
13             return False
14         # write code here