1、raw_input()默认接受的是字符串，而后边需要的数字，所以就需要进行类型转换。
2、rom functools import reducedef str2float(s): def f(s): return {&#泌驾台佐39;0': 0, '1': 1, '2': 2, '3': 3, '4': 4, '5': 5, '6': 6, '7': 7, '8': 8, '9': 9, '.': '.'}[s] def g(x, y): return x*10 + y
3、pos = s.find('.')
4、 front = reduce(g,map(f,s[0:pos]))
5、 rear = reduce(g,map(f,s[pos+1:]))/10**(len(s)-pos-1)return front+rear
6、print('str2float(\'123.456\') =', str2float('123.456'))
