利用map和reduce编写一个str2float函数

 1 from functools import reduce
 2 def str2float(s):
 3     def char2num(s):
 4         digits = {‘0‘: 0, ‘1‘: 1, ‘2‘: 2, ‘3‘: 3, ‘4‘: 4, ‘5‘: 5, ‘6‘: 6, ‘7‘: 7, ‘8‘: 8, ‘9‘: 9,‘.‘:11}
           #11只是一个标记
 5         return digits[s]
 6     r=list(map(char2num,s)) 
 7  8     def plus(x,y):
 9           if y!=11:
10               return x*10+y
11           else:
12               return x
13     return reduce(plus,r)*10**-(len(s)-s.index(‘.‘)-1)

1     def char2num(s):
2         digits = {‘0‘: 0, ‘1‘: 1, ‘2‘: 2, ‘3‘: 3, ‘4‘: 4, ‘5‘: 5, ‘6‘: 6, ‘7‘: 7, ‘8‘: 8, ‘9‘: 9}
3         return digits[s]
      #计算小数点位数
4     dot=len(s)-s.index(‘.‘)-1
      #将小数点替换掉
5     new_s=s.replace(‘.‘,‘‘)
6     r=list(map(char2num,new_s)) 
7     def plus(x,y):
8           return x*10+y
9     return reduce(plus,r)*10**-dot