利用map和reduce编写一个str2float函数，把字符串'123.456'转换成浮点数123.456：

# -*- coding: utf-8 -*-
from functools import reduce

def str2float(s):

DIGITS = {‘0‘: 0, ‘1‘: 1, ‘2‘: 2, ‘3‘: 3, ‘4‘: 4, ‘5‘: 5, ‘6‘: 6, ‘7‘: 7, ‘8‘: 8, ‘9‘: 9}
def fn1(x, y):
return x * 10 + y
def fn2(i,j):
return 0.1*i+j
def char2num(s):
return DIGITS[s]
m= s.split(‘.‘)[0]
n= s.split(‘.‘)[1]
m1=list(map(char2num,m))
n1=list(map(char2num,n))[::-1]
print(n1)
return reduce(fn1, m1)+reduce(fn2,n1)*0.1

print(‘str2float(\‘123.456\‘) =‘, str2float(‘123.456‘))
if abs(str2float(‘123.456‘) - 123.456) < 0.00001:
    print(‘测试成功!‘)
else:
    print(‘测试失败!‘)