def char2num(s):

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

     return digits[s]

def str2float(s):

     l1 ,l2 = s.split('.')

     l11 = reduce(lambda x , y :10*x + y ,map(char2num,l1))

     l22 = reduce(lambda x , y :10*x + y,map(char2num,l2))

     return l11+l22*10**(-len(l2))