python map reduce 将浮点字符串转为浮点数

from functools import reducedef str2float(s):    return reduce(lambda x,y:x+int2dec(y),map(str2int,s.split('.')))   #map + reducedef char2num(s):    return {'0':0,'1':1,'2':2,'3':3,'4':4,'5':5,'6':6,'7':7,'8':8,'9':9}[s]def str2int(s):    return reduce(lambda x,y:x*10+y,map(char2num,s))def intLen(i):    return len('%d'%i)def int2dec(i):    return float(i)/(10**intLen(i))print(str2float('123.456'))