python字符串转换成数字int的函数

#!/usr/bin/env python
# -*- coding: utf-8 -*-

def str2int(s):
    def fn(x,y):
        return x * 10 + y
    def char2num(s):
        return {'0': 0, '1': 1, '2': 2, '3': 3, '4': 4, '5': 5, '6': 6, '7': 7, '8': 8, '9': 9}[s]
    return reduce(fn,map(char2num,s))
print str2int('12312346123')