from functools import reducedef str2float(s):    DIGITS = {'0':0,'1':1,'2':2,'3':3,'4':4,'5':5,'6':6,'7':7,'8':8,'9':9}    def char2int(char):        return DIGITS[char]    a=reduce(lambda x,y:x*10+y,map(char2int,s[:s.index('.')]))    b=reduce(lambda x,y:x*10+y,map(char2int,s[s.index('.')+1:]))*pow(10,-len(s[s.index('.')+1:]))    return a+bprint(str2float('123.4567'))