from functools import reduce       

def char2num(s):

    digitals = {'0':0, '1':1, '2':2, '3':3, '4':4, '5':5, '6':6, '7':7, '8':8, '9':9}

    return digitals[s]

def str2float(s):

    index = len(s) - s.rfind('.') - 1

    r = s.replace('.','')

    return reduce(lambda x, y: x *10 + y, map(char2num, r))/10**index