Python string to floating point function to share

Write a str2float function using map and reduce to convert the string '123.456' to the floating point number 123.456

from functools import reduce
 
def str2float(s):
  return reduce(lambda x,y:x+int2dec(y),map(str2int,('.')))
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]
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 i/(10**intLen(i))
   
print(str2float('123.456'))

This is the whole content of this code, I hope it can help you to learn Python.